UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM N-CSR

                   CERTIFIED SHAREHOLDER REPORT OF REGISTERED
                        MANAGEMENT INVESTMENT COMPANIES



		Investment Company Act file number 811-05099

                          Pioneer Money Market Trust
               (Exact name of registrant as specified in charter)


                       60 State Street, Boston, MA 02109
              (Address of principal executive offices) (ZIP code)


            Terrence J. Cullen, Pioneer Investment Management, Inc.,
                       60 State Street, Boston, MA 02109
                    (Name and address of agent for service)


Registrant's telephone number, including area code:  (617) 742-7825


Date of fiscal year end:  December 31


Date of reporting period:  January 1, 2017 through June 30, 2017


Form N-CSR is to be used by management investment companies to file reports with
the Commission not later than 10 days after the transmission to stockholders of
any report that is required to be transmitted to stockholders under Rule 30e-1
under the Investment Company Act of 1940 (17 CFR 270.30e-1).  The Commission may
use the information provided on Form N-CSR in its regulatory, disclosure review,
inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-CSR,
and the Commission will make this information public. A registrant is not
required to respond to the collection of information contained in Form N-CSR
unless the Form displays a currently valid Office of Management and Budget
("OMB") control number. Please direct comments concerning the accuracy of the
information collection burden estimate and any suggestions for reducing the
burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW,
Washington, DC 20549-0609.  The OMB has reviewed this collection of information
under the clearance requirements of 44 U.S.C. ss. 3507.


ITEM 1. REPORTS TO STOCKHOLDERS.


                        Pioneer U.S. Government
                        Money Market Fund

--------------------------------------------------------------------------------
                        Semiannual Report | June 30, 2017
--------------------------------------------------------------------------------

                        Ticker Symbols:
                        Class A  PMTXX
                        Class Y  PRYXX

                        [LOGO]   Amundi Pioneer
                                 ==============
                               ASSET MANAGEMENT



                        visit us: www.amundipioneer.com


Table of Contents


                                                                           
President's Letter                                                             2

Portfolio Management Discussion                                                4

Portfolio Summary                                                              7

Prices and Distributions                                                       8

Comparing Ongoing Fund Expenses                                               10

Schedule of Investments                                                       12

Financial Statements                                                          16

Notes to Financial Statements                                                 22

Additional Information                                                        29

Approval of New and Interim Management Agreements                             31

Trustees, Officers and Service Providers                                      40


       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 1


President's Letter

U.S. markets have continued to generate positive returns during the first
several months of 2017, with so-called "risk" assets, such as equities and
credit-sensitive bonds, posting solid gains. U.S. equities, as measured by the
Standard & Poor's 500 Index, returned slightly more than 6% in the first
calendar quarter of the year and more than 3% for the second quarter. Meanwhile,
high-yield securities have dominated bond market performance thus far in 2017.

The post-election market momentum we witnessed in the U.S. during the final
weeks of the fourth quarter of 2016 slowed only when oil prices slumped in
March, due to both higher-than-expected inventories and concerns over whether
OPEC (Organization of Petroleum Exporting Countries) would continue its supply
cuts. Not even the Federal Reserve System's (the Fed's) two rate hikes since
March, nor Britain's trigger of Article 50 to begin the "Brexit" process caused
any dramatic sell-off of risk assets. In fact, we are encouraged by the more
hawkish stance of the Fed with regard to interest rates, in light of our view
that current U.S. bond yields do not fairly reflect the prospective levels of
economic activity and inflation. We expect the Fed to continue to tighten
monetary policy, with at least one more rate hike likely to occur before the end
of 2017.

While U.S. gross domestic product (GDP) did slow in the first quarter, ending up
at 1.4% after revisions, the expectation is for GDP growth to pick-up in the
second quarter, with a solid consumer leading the way. It is our view that the
U.S. economy may lead all developed nations in 2017, with GDP growth in excess
of 2% for the full year, even if proposed tax and regulatory reforms are not
passed into law in the near future. We also believe solid domestic employment
figures should continue to support consumption and the housing market, and that
stronger corporate profits and increased government spending may contribute to
economic growth in 2018 and beyond. In addition, as we monitor global Purchasing
Manager Indices (PMIs), we note that their numbers are increasing, which
suggests that growth in global economies is also improving. (PMIs are used to
measure the economic health of the manufacturing sector.)

There are, as always, some risks to our outlook. First, the market already has
priced in a good deal of the Trump economic reform platform, and that could lead
to near-term disappointment if Congressional follow-through does not happen this
year. The future of the Affordable Care Act (ACA) is another potential concern,
as Congressional leaders have, thus far, failed to generate

2 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


enough support to get new health care legislation approved by both houses.
However, if a bill is eventually passed that either eliminates or significantly
alters the ACA, the new law will undoubtedly have an effect on the health care
sector, one of the largest segments of the U.S. economy. Geopolitical risks, of
course, remain a potential headwind, given ongoing strife in the Middle East and
renewed tensions on the Korean Peninsula.

While our current outlook is generally optimistic, conditions can and often do
change, and while passive investment strategies may have a place in one's
overall portfolio, it is our view that all investment decisions are active
choices.

Throughout our history, we have believed in the importance of active management.
The active decisions to invest in equities or fixed-income securities are made
by a team of experienced investment professionals focusing on identifying value
across global markets using proprietary research, careful risk management, and a
long-term perspective. We believe our shareowners can benefit from the
experience and tenure of our investment teams as well as the insights generated
from our extensive research process.

As always, and particularly during times of market uncertainty, we encourage you
to work with your financial advisor to develop an overall investment plan that
addresses both your short- and long-term goals, and to implement such a plan in
a disciplined manner.

We greatly appreciate the trust you have placed in us and look forward to
continuing to serve you in the future.

Sincerely,

/s/ Lisa M. Jones

Lisa M. Jones
Head of the Americas, President and CEO of US
Amundi Pioneer Asset Management USA, Inc.
June 30, 2017

Any information in this shareowner report regarding market or economic trends or
the factors influencing the Fund's historical or future performance are
statements of opinion as of the date of this report. Past performance is no
guarantee of future results.

       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 3


Portfolio Management Discussion | 6/30/17

Important Note: On July 3, 2017, Amundi acquired Pioneer Investments, a group of
asset management companies located throughout the world. Amundi, one of the
world's largest asset managers, is headquartered in Paris, France. As a result
of the transaction, Pioneer Investment Management, Inc., the Fund's investment
adviser, became an indirect wholly owned subsidiary of Amundi and Amundi's
wholly owned subsidiary, Amundi USA, Inc. Prior to July 3, 2017, Pioneer
Investments was owned by Pioneer Global Asset Management S.p.A., a wholly owned
subsidiary of UniCredit S.p.A.

In connection with the transaction, the names of the Fund's investment adviser
and principal underwriter changed. Effective July 3, 2017, the name of Pioneer
Investment Management, Inc. changed to Amundi Pioneer Asset Management, Inc. and
the name of Pioneer Funds Distributor, Inc. changed to Amundi Pioneer
Distributor, Inc.

This transaction does not impact your existing relationship with Pioneer
Investments, your advisor, or the methods you use to communicate with us, as the
investor contact telephone numbers and services you expect will remain the same.
We are excited, however, to be launching a new website representing the combined
company. Come visit us at: www.amundipioneer.com.

Money market interest rates crept higher during the six-month period ended June
30, 2017, as the U.S. Federal Reserve (the Fed) gradually hiked the key Federal
funds rate. In the following discussion, Seth Roman reviews the factors that
affected the performance of Pioneer U.S. Government Money Market Fund during the
six-month period. Mr. Roman, a vice president and a portfolio manager at Amundi
Pioneer Asset Management, Inc. ("Amundi Pioneer"), is responsible for the daily
management of the Fund.

Q    How did the Fund perform during the six-month period ended June 30, 2017?

A    Pioneer U.S. Government Money Market Fund's Class A shares returned 0.06%
     at net asset value during the six-month period ended June 30, 2017. During
     the same period, the average return of the 170 mutual funds in Lipper's
     U.S. Government Money Market Funds Category was 0.09%.

Q    How would you describe the environment for money market investing during
     the six-month period ended June 30, 2017?

A    Interest rates in the short-term money market moved higher over the six
     months. Following an increase of 0.25% at the end of 2016, the Fed hiked
     the influential Fed funds rate twice more during the six-month period --
     once in March and again in June. At the end of the period, the Fed's target
     rate for Fed funds was 1.00% to 1.25%.

4 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


     Over the period, U.S. gross domestic product (GDP) maintained its modest
     annual growth rate of approximately 2%, despite a slight downturn in GDP in
     the first quarter, as new-job creation expanded at a robust pace and the
     housing market continued to gain momentum. Wage inflation, however, did not
     increase by as much as expected given an improving economy that had been
     rebounding for several years. As a consequence, the Fed hinted that, while
     it still planned to raise rates further in 2017 and 2018, some hikes might
     be delayed a bit if wage growth remains sluggish.

Q    How did you manage the Fund's portfolio in that environment during the
     six-month period ended June 30, 2017?

A    Throughout the period, we held to the Fund's primary objective, which is to
     protect shareholders' capital by maintaining a stable net asset value of
     $1.00 per share. We maintained a conservative positioning in the portfolio
     with regard to interest-rate sensitivity during the six-month period, even
     as we adjusted the Fund's average effective duration from 21 days to about
     30 days. (Duration is a measure of the sensitivity of the price, or the
     value of principal, of a fixed-income investment to a change in interest
     rates, expressed as a number of years.) The longer duration, a move which
     we did not consider significant, was designed to increase the Fund's
     ability to capture additional interest income as short-term interest rates
     moved higher and as longer-dated securities began offering slightly more
     yield. At the same time, we also remained focused on the Fund's secondary
     objective, which is to maintain sufficient liquidity so that investors have
     access to their money. To maintain liquidity, we emphasized two types of
     holdings in the portfolio: tri-party repurchase agreements, which are
     overnight loans collateralized by either U.S. Treasuries or U.S. agency
     securities, and shorter-maturity U.S. Treasury bills with maturity dates of
     one month or less.

     While we continued to concentrate on the Fund's objectives of safety and
     liquidity, we did attempt to find additional income, where and when it was
     available. Among the investment vehicles we used to seek out additional
     income were U.S. Treasury floaters, which have daily resets of their
     interest rates and have the potential to offer slightly increasing yields
     over time as the Fed raises interest rates.

     Overall, the greatest concentration within the Fund's total investment
     portfolio during the period, including Treasury floaters, was in securities
     directly backed by the U.S. government, such as U.S. Treasury bills and
     notes.

Q    Did the Fund's yield change during the six-month period ended June 30,
     2017?

A    The Fund's yield did move up somewhat as the Fed raised interest rates.

       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 5


Q    What is your investment outlook?

A    Midway through the year, we are somewhat skeptical that the Federal
     government soon will add any significant fiscal stimulus to the economy,
     either through tax reform or infrastructure investment. Given that view, we
     think the economy is likely to continue to expand at a slow rate, with GDP
     staying close to an annualized growth rate of about 2%. Inflation remains
     well under control, with wage inflation staying below expectations.

     As we discussed, while the Fed continues to plan further rate hikes, it
     also has signaled that it is watching for more evidence of rising wage
     inflation, and it is therefore possible that some anticipated rate
     increases may be delayed, although the Fed will likely be careful not to
     send out any signals suggesting that the economy is weakening.

     Six of the Fund's 10 largest positions as of June 30, 2017, were U.S.
     Treasury floaters. Going forward, we intend to maintain a healthy exposure
     in the portfolio to floating-rate securities in an effort to capture
     additional yield opportunities, but we will maintain our primary focus on
     capital preservation.

Please refer to the Schedule of Investments on pages 12-15 for a full listing of
Fund securities.

You could lose money by investing in the Fund. Although the Fund seeks to
preserve the value of your investment at $1.00 per share, it cannot guarantee it
will do so. The Fund may impose a fee upon the sale of your shares or may
temporarily suspend your ability to sell shares if the Fund's liquidity falls
below required minimums because of market conditions or other factors. An
investment in the Fund is not insured or guaranteed by the Federal Deposit
Insurance Corporation or any other government agency. The Fund's sponsor has no
legal obligation to provide financial support to the Fund, and you should not
expect that the sponsor will provide financial support to the Fund at any time.

All investments are subject to risk, including the possible loss of principal.
In the past several years, financial markets have experienced increased
volatility, depressed valuations, decreased liquidity and heightened
uncertainty. These conditions may continue, recur, worsen or spread.

The securities issued by U.S. Government-sponsored entities (e.g., FNMA, Freddie
Mac) are neither guaranteed nor issued by the U.S. Government.

At times, the Fund's investments may represent industries or industry sectors
that are interrelated or have common risks, making it more susceptible to any
economic, political, or regulatory developments or other risks affecting those
industries and sectors.

These risks may increase share price volatility.

Before investing, consider the product's investment objectives, risks, charges
and expenses. Contact your advisor or Amundi Pioneer Asset Management, Inc., for
a prospectus or summary prospectus containing this information. Read it
carefully. Any information in this shareholder report regarding market or
economic trends or the factors influencing the Fund's historical or future
performance are statements of opinion as of the date of this report. Past
performance is no guarantee of future results.

6 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


Portfolio Summary | 6/30/17

Portfolio Diversification
--------------------------------------------------------------------------------
(As a percentage of total investment portfolio)

[THE FOLLOWING DATA WAS REPRESENTED AS A PIE CHART IN THE PRINTED MATERIAL]



                                                                        
U.S. Government Securities                                                 90.8%
Repurchase Agreements (Collateralized by U.S. Government Securities)        9.2%


10 Largest Holdings
--------------------------------------------------------------------------------
(As a percentage of long-term holdings)*



                                                                       
 1. U.S. Treasury Bills, 7/6/17                                           11.41%
--------------------------------------------------------------------------------
 2. U.S. Treasury Bills, 7/13/17                                          11.11
--------------------------------------------------------------------------------
 3. U.S. Treasury Bills, 9/28/17                                          10.36
--------------------------------------------------------------------------------
 4. U.S. Treasury Bills, 7/20/17                                           9.76
--------------------------------------------------------------------------------
 5. U.S. Treasury Note, Floating Rate Note, 7/31/17                        5.94
--------------------------------------------------------------------------------
 6. U.S. Treasury Note, Floating Rate Note, 4/30/18                        5.60
--------------------------------------------------------------------------------
 7. U.S. Treasury Note, Floating Rate Note, 1/31/18                        5.52
--------------------------------------------------------------------------------
 8. U.S. Treasury Note, Floating Rate Note, 10/31/18                       2.86
--------------------------------------------------------------------------------
 9. U.S. Treasury Note, Floating Rate Note, 7/31/18                        2.85
--------------------------------------------------------------------------------
10. U.S. Treasury Note, Floating Rate Note, 10/31/17                       2.29
--------------------------------------------------------------------------------


*    The Fund is actively managed, and current holdings may be different. The
     holdings listed should not be considered recommendations to buy or sell any
     security listed.

       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 7


Prices and Distributions | 6/30/17

Net Asset Value per Share
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
         Class                     6/30/17                              12/31/16
--------------------------------------------------------------------------------
                                                                    
          A                         $1.00                                 $1.00
--------------------------------------------------------------------------------
          Y                         $1.00                                 $1.00
--------------------------------------------------------------------------------


Distributions per Share: 1/1/17 - 6/30/17
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
                                               Short-Term            Long-Term
        Class           Dividends             Capital Gains        Capital Gains
--------------------------------------------------------------------------------
                                                             
         A               $0.0006                 $    --              $    --
--------------------------------------------------------------------------------
         Y               $0.0010                 $    --              $    --
--------------------------------------------------------------------------------


Yields
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
          Class                7-Day Annualized                 7-Day Effective*
--------------------------------------------------------------------------------
                                                              
           A                        0.34%                           0.34%
--------------------------------------------------------------------------------
           Y                        0.49%                           0.49%
--------------------------------------------------------------------------------


*    Assumes daily compounding of dividends.

8 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


Expense Ratio (Per prospectus dated August 1, 2017)
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
                   Class                             Gross
--------------------------------------------------------------------------------
                                                  
                     A                               0.82%
--------------------------------------------------------------------------------
                     Y                               0.50%
--------------------------------------------------------------------------------


Call 1-800-225-6292 or visit www.amundipioneer.com for the most recent month-end
performance results. Current performance may be lower or higher than the
performance data quoted.

The performance data quoted represents past performance, which is no guarantee
of future results.

Investment return and principal value will fluctuate, and shares, when redeemed,
may be worth more or less than their original cost.

Amundi Pioneer has agreed to limit the Fund's expenses for any class of shares
or waive a portion of its management fee in an effort to maintain a net asset
value of $1.00 per share. From time to time, Amundi Pioneer and its affiliates
may limit the expenses of one or more classes for the purpose of avoiding a
negative yield or increasing its yield during the period of the limitation.
These expense limitation policies are voluntary and temporary and may be revised
or terminated by Amundi Pioneer at any time without notice.

Performance does not reflect the deduction of taxes that a shareowner would pay
on Fund distributions or the redemption of Fund shares.

       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 9


Comparing Ongoing Fund Expenses

As a shareowner in the Fund, you incur two types of costs:

(1)  ongoing costs, including management fees, distribution and/or service
     (12b-1) fees, and other Fund expenses; and

(2)  transaction costs, including sales charges (loads) on purchase payments.

This example is intended to help you understand your ongoing expenses (in
dollars) of investing in the Fund and to compare these costs with the ongoing
costs of investing in other mutual funds. The example is based on an investment
of $1,000 at the beginning of the Fund's latest six-month period and held
throughout the six months.

Using the Tables
--------------------------------------------------------------------------------
Actual Expenses

The first table below provides information about actual account values and
actual expenses. You may use the information in this table, together with the
amount you invested, to estimate the expenses that you paid over the period as
follows:

(1)  Divide your account value by $1,000
     Example: an $8,600 account value (divided by) $1,000 = 8.6

(2)  Multiply the result in (1) above by the corresponding share class's number
     in the third row under the heading entitled "Expenses Paid During Period"
     to estimate the expenses you paid on your account during this period.

Expenses Paid on a $1,000 Investment in Pioneer U.S. Government Money Market

Based on actual returns from January 1, 2017, through June 30, 2017.



--------------------------------------------------------------------------------
Share Class                                         A                      Y
--------------------------------------------------------------------------------
                                                                 
Beginning Account Value                         $1,000.00              $1,000.00
Value on 1/1/17
--------------------------------------------------------------------------------
Ending Account                                  $1,000.60              $1,001.00
Value on 6/30/17
--------------------------------------------------------------------------------
Expenses Paid                                   $    2.98              $    2.58
During Period*
--------------------------------------------------------------------------------


*    Expenses are equal to the Fund's annualized net expense ratio of 0.60% and
     0.52% for Class A and Class Y shares, respectively, multiplied by the
     average account value over the period, multiplied by 181/365 (to reflect
     the one-half year period).

10 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


Hypothetical Example for Comparison Purposes

The table below provides information about hypothetical account values and
hypothetical expenses based on the Fund's actual expense ratio and an assumed
rate of return of 5% per year before expenses, which is not the Fund's actual
return. The hypothetical account values and expenses may not be used to estimate
the actual ending account balance or expenses you paid for the period.

You may use this information to compare the ongoing costs of investing in the
Fund and other funds. To do so, compare this 5% hypothetical example with the 5%
hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the tables are meant to highlight your
ongoing costs only and do not reflect any transaction costs, such as sales
charges (loads) that are charged at the time of the transaction. Therefore, the
table below is useful in comparing ongoing costs only and will not help you
determine the relative total costs of owning different funds. In addition, if
these transaction costs were included, your costs would have been higher.

Expenses Paid on a $1,000 Investment in Pioneer U.S. Government Money Market

Based on a hypothetical 5% per year return before expenses, reflecting the
period from January 1, 2017, through June 30, 2017.



--------------------------------------------------------------------------------
Share Class                                       A                        Y
--------------------------------------------------------------------------------
                                                                 
Beginning Account                             $1,000.00                $1,000.00
Value on 1/1/17
--------------------------------------------------------------------------------
Ending Account                                $1,021.82                $1,022.22
Value on 6/30/17
--------------------------------------------------------------------------------
Expenses Paid                                 $    3.01                $    2.61
During Period*
--------------------------------------------------------------------------------


*    Expenses are equal to the Fund's annualized net expense ratio of 0.60% and
     0.52% for Class A and Class Y shares, respectively, multiplied by the
     average account value over the period, multiplied by 181/365 (to reflect
     the one-half year period).

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 11


Schedule of Investments | 6/30/17 (unaudited)



--------------------------------------------------------------------------------------------
               Floating
Principal      Rate (a)
Amount ($)     (unaudited)                                                      Value
--------------------------------------------------------------------------------------------
                                                                       
                             U.S. GOVERNMENT AND AGENCY
                             OBLIGATIONS -- 90.7%
     750,000                 Federal Farm Credit Banks, 5.55%, 8/1/17           $    752,685
     250,000          1.17   Federal Farm Credit Banks, Floating Rate Note,
                             7/14/17                                                 250,021
     655,000          1.26   Federal Farm Credit Banks, Floating Rate Note,
                             8/29/17                                                 655,260
     280,000          1.23   Federal Farm Credit Banks, Floating Rate Note,
                             10/17/17                                                280,173
   2,000,000          1.25   Federal Farm Credit Banks, Floating Rate Note,
                             12/18/17                                              2,002,114
   1,250,000          1.11   Federal Farm Credit Banks, Floating Rate Note,
                             1/8/18                                                1,251,192
   2,000,000          1.18   Federal Farm Credit Banks, Floating Rate Note,
                             5/9/18                                                2,006,056
     400,000          1.23   Federal Farm Credit Banks, Floating Rate Note,
                             7/6/18                                                  401,005
   1,000,000                 Federal Home Loan Bank Discount Notes,
                             7/5/17 (b)                                              999,950
     300,000                 Federal Home Loan Bank Discount Notes,
                             8/2/17 (b)                                              299,779
     700,000                 Federal Home Loan Bank Discount Notes,
                             8/11/17 (b)                                             699,295
   1,000,000                 Federal Home Loan Banks, 0.875%, 7/3/17               1,000,000
   2,220,000                 Federal Home Loan Banks, 0.7%, 7/27/17                2,219,764
     750,000                 Federal Home Loan Banks, 1.0%, 9/22/17                  750,134
     300,000                 Federal Home Loan Banks, 0.875%, 3/1/18                 299,853
     300,000                 Federal Home Loan Banks, 1.125%, 4/25/18                299,884
   1,000,000          1.13   Federal Home Loan Banks, Floating Rate Note,
                             7/27/17                                                 999,996
   1,500,000          1.17   Federal Home Loan Banks, Floating Rate Note,
                             8/15/17                                               1,500,000
     750,000          1.16   Federal Home Loan Banks, Floating Rate Note,
                             8/23/17                                                 750,298
   1,630,000          1.17   Federal Home Loan Banks, Floating Rate Note,
                             8/25/17                                               1,630,717
   5,000,000          1.30   Federal Home Loan Banks, Floating Rate Note,
                             11/2/17                                               5,001,277
   1,500,000          1.24   Federal Home Loan Banks, Floating Rate Note,
                             12/1/17                                               1,500,099
   1,500,000          1.15   Federal Home Loan Banks, Floating Rate Note,
                             12/7/17                                               1,500,230
   2,600,000          1.18   Federal Home Loan Banks, Floating Rate Note,
                             2/5/18                                                2,603,601
   1,455,000                 Federal Home Loan Mortgage Corp., 1.0%, 9/29/17       1,454,738
     300,000                 Federal Home Loan Mortgage Corp., 0.875%,
                             3/7/18                                                  299,458


The accompanying notes are an integral part of these financial statements.

12 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17




--------------------------------------------------------------------------------------------
               Floating
Principal      Rate (a)
Amount ($)     (unaudited)                                                      Value
--------------------------------------------------------------------------------------------
                                                                       
                             U.S. GOVERNMENT AND AGENCY
                             OBLIGATIONS -- (continued)
   3,000,000          1.34   Federal Home Loan Mortgage Corp., Floating
                             Rate Note, 7/21/17                                 $  3,000,051
   4,410,000          1.17   Federal Home Loan Mortgage Corp., Floating
                             Rate Note, 11/13/17                                   4,412,157
   1,200,000          1.13   Federal Home Loan Mortgage Corp., Floating
                             Rate Note, 1/8/18                                     1,201,784
   2,510,000                 Federal National Mortgage Association, 0.875%,
                             8/28/17                                               2,509,803
   1,200,000                 Federal National Mortgage Association, 1.0%,
                             9/20/17                                               1,200,188
   1,458,000                 Federal National Mortgage Association, 1.0%,
                             9/27/17                                               1,457,708
     460,000                 Federal National Mortgage Association, 0.875%,
                             10/26/17                                                460,171
     300,000                 Federal National Mortgage Association, 1.0%,
                             11/27/17                                                299,977
     300,000                 Federal National Mortgage Association, 0.875%,
                             3/28/18                                                 299,440
     735,000                 Federal National Mortgage Association, 0.875%,
                             5/21/18                                                 732,772
   5,045,000          1.23   Federal National Mortgage Association, Floating
                             Rate Note, 7/20/17                                    5,045,470
     420,000          1.09   Federal National Mortgage Association, Floating
                             Rate Note, 10/5/17                                      420,023
   1,300,000          1.13   Federal National Mortgage Association, Floating
                             Rate Note, 1/11/18                                    1,301,951
  30,000,000                 U.S. Treasury Bills, 7/6/17 (b)                      29,998,036
  29,225,000                 U.S. Treasury Bills, 7/13/17 (b)                     29,217,956
  25,665,000                 U.S. Treasury Bills, 7/20/17 (b)                     25,655,031
   1,500,000                 U.S. Treasury Bills, 7/27/17 (b)                      1,499,220
   1,860,000                 U.S. Treasury Bills, 8/3/17 (b)                       1,858,636
   1,040,000                 U.S. Treasury Bills, 8/10/17 (b)                      1,039,031
   3,000,000                 U.S. Treasury Bills, 8/17/17 (b)                      2,997,853
     615,000                 U.S. Treasury Bills, 8/31/17 (b)                        614,190
     295,000                 U.S. Treasury Bills, 9/7/17 (b)                         294,470
   3,000,000                 U.S. Treasury Bills, 9/14/17 (b)                      2,996,445
  27,305,000                 U.S. Treasury Bills, 9/28/17 (b)                     27,239,635
   3,000,000                 U.S. Treasury Bills, 10/12/17 (b)                     2,994,651
   2,260,000                 U.S. Treasury Bills, 10/26/17 (b)                     2,253,105
     750,000                 U.S. Treasury Bills, 11/2/17 (b)                        747,471
     300,000                 U.S. Treasury Bills, 11/9/17 (b)                        299,188
     635,000                 U.S. Treasury Bills, 12/7/17 (b)                        632,664
     300,000                 U.S. Treasury Bills, 3/1/18 (b)                         298,112
     600,000                 U.S. Treasury Bills, 4/26/18 (b)                        594,716


The accompanying notes are an integral part of these financial statements.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 13


Schedule of Investments | 6/30/17 (unaudited) (continued)



--------------------------------------------------------------------------------------------
               Floating
Principal      Rate (a)
Amount ($)     (unaudited)                                                      Value
--------------------------------------------------------------------------------------------
                                                                       
                             U.S. GOVERNMENT AND AGENCY
                             OBLIGATIONS -- (continued)
  15,615,000          1.08   U.S. Treasury Note, Floating Rate Note, 7/31/17    $ 15,615,836
   6,005,000          1.17   U.S. Treasury Note, Floating Rate Note, 10/31/17      6,008,318
  14,485,000          1.27   U.S. Treasury Note, Floating Rate Note, 1/31/18      14,503,971
  14,715,000          1.19   U.S. Treasury Note, Floating Rate Note, 4/30/18      14,732,380
   7,495,000          1.18   U.S. Treasury Note, Floating Rate Note, 7/31/18       7,503,644
   7,495,000          1.17   U.S. Treasury Note, Floating Rate Note, 10/31/18      7,509,452
   1,485,000          1.14   U.S. Treasury Note, Floating Rate Note, 1/31/19       1,487,228
   3,000,000          1.07   U.S. Treasury Note, Floating Rate Note, 4/30/19       3,000,721
     625,000                 U.S. Treasury Notes, 0.875%, 8/15/17                    625,162
   1,330,000                 U.S. Treasury Notes, 0.625%, 8/31/17                  1,329,331
   1,030,000                 U.S. Treasury Notes, 1.875%, 8/31/17                  1,031,532
     880,000                 U.S. Treasury Notes, 1.875%, 9/30/17                    882,235
   1,035,000                 U.S. Treasury Notes, 0.625%, 11/30/17                 1,033,920
   1,020,000                 U.S. Treasury Notes, 2.25%, 11/30/17                  1,025,405
     785,000                 U.S. Treasury Notes, 1.0%, 12/15/17                     785,554
     295,000                 U.S. Treasury Notes, 0.75%, 1/31/18                     294,400
     295,000                 U.S. Treasury Notes, 0.75%, 4/30/18                     294,014
     300,000                 U.S. Treasury Notes, 1.0%, 5/15/18                      299,500
--------------------------------------------------------------------------------------------
                             TOTAL U.S. GOVERNMENT AND
                             AGENCY OBLIGATIONS
                             (Cost $262,942,087)                                $262,942,087
--------------------------------------------------------------------------------------------
                             TEMPORARY CASH INVESTMENTS -- 9.2%
                             REPURCHASE AGREEMENTS -- 9.2%
  14,410,000                 $14,410,000 ScotiaBank, 1.12%,
                             dated 6/30/17 plus accrued interest on
                             7/3/17 collateralized by the following:
                             $85,250 Federal Home Loan Mortgage
                             Corp., 1.44%, 3/29/19,
                             $5,113,776 Freddie Mac Giant,
                             3.14% - 5.5%, 10/1/35 - 4/1/47,
                             $9,441,146 Federal National Mortgage
                             Association, 3.0% - 4.5%, 2/1/29 - 5/1/47,
                             $59,401 Government National Mortgage
                             Association, 2.25% - 3.0%, 11/20/39 - 7/20/46      $ 14,410,000
   6,150,000                 $6,150,000 TD Securities USA LLC, 1.10%,
                             dated 6/30/17 plus accrued interest on
                             7/3/17 collateralized by the following:
                             $3,020,223 Federal National Mortgage
                             Association, 3.5% - 6.625%, 11/15/30 - 12/1/46,
                             $3,252,795 U.S. Treasury Notes, 0.0% - 1.5%,
                             7/20/17 - 1/31/19                                     6,150,000


The accompanying notes are an integral part of these financial statements.

14 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17




--------------------------------------------------------------------------------------------
               Floating
Principal      Rate (a)
Amount ($)     (unaudited)                                                      Value
--------------------------------------------------------------------------------------------
                                                                          
                             REPURCHASE AGREEMENTS -- (continued)
   6,150,000                 $6,150,000 TD Securities USA LLC, 1.12%,
                             dated 6/30/17 plus accrued interest on
                             7/3/17 collateralized by the following:
                             $6,273,095 U.S. Treasury Notes, 0.0% - 2.5%,
                             7/20/17 - 8/15/23                                  $  6,150,000
                                                                                ------------
                                                                                $ 26,710,000
--------------------------------------------------------------------------------------------
                             TOTAL TEMPORARY CASH INVESTMENTS
                             (Cost $26,710,000)                                 $ 26,710,000
--------------------------------------------------------------------------------------------
                             TOTAL INVESTMENT IN SECURITIES -- 99.9%
                             (Cost $289,652,087) (c)                            $289,652,087
--------------------------------------------------------------------------------------------
                             OTHER ASSETS & LIABILITIES -- 0.1%                 $    299,923
--------------------------------------------------------------------------------------------
                             NET ASSETS -- 100.0%                               $289,952,010
============================================================================================


(a)         Debt obligation with a variable interest rate. Rate shown is rate at
            end of period.

(b)         Security issued with a zero coupon. Income is recognized through
            accretion of discount.

(c)         At June 30, 2017, cost for federal income tax purposes was
            $289,652,087.

The Fund is permitted to engage in purchase and sale transactions ("cross
trades") with certain funds and accounts for which Amundi Pioneer Asset
Management, Inc. (Amundi Pioneer), formerly Pioneer Investment Management, Inc.
(PIM), serves as the Fund's investment adviser, as set forth in Rule 17a-7 under
the Investment Company Act of 1940, pursuant to procedures adopted by the Board
of Trustees. Under these procedures, cross trades are effected at current market
prices. During the six months ended June 30, 2017, the Fund did not engage in
cross trade activity.

Various inputs are used in determining the value of the Fund's investments.
These inputs are summarized in the three broad levels below.

  Level 1 - quoted prices in active markets for identical securities.

  Level 2 - other significant observable inputs (including quoted prices for
            similar securities, interest rates, prepayment speeds, credit risks,
            etc.). See Notes to Financial Statements -- Note 1A.

  Level 3 - significant unobservable inputs (including the Fund's own
            assumptions in determining fair value of investments). See Notes to
            Financial Statements -- Note 1A.

The following is a summary of the inputs used as of June 30, 2017, in valuing
the Fund's investments:



--------------------------------------------------------------------------------
                                  Level 1  Level 2        Level 3   Total
--------------------------------------------------------------------------------
                                                        
U.S. Government and
   Agency Obligations             $  --    $262,942,087   $  --     $262,942,087
Repurchase Agreements                --      26,710,000      --       26,710,000
--------------------------------------------------------------------------------
Total                             $  --    $289,652,087   $  --     $289,652,087
================================================================================


During the six months ended June 30, 2017, there were no transfers between
Levels 1, 2 and 3.

The accompanying notes are an integral part of these financial statements.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 15


Statement of Assets and Liabilities | 6/30/17 (unaudited)



                                                                 
ASSETS:
  Investment in securities (cost $262,942,087)                      $262,942,087
  Repurchase agreements (cost $26,710,000)                            26,710,000
--------------------------------------------------------------------------------
  Total investment in securities, at value (cost $289,652,087)       289,652,087
  Cash                                                                   449,490
  Receivables --
     Fund shares sold                                                    123,771
     Interest                                                            250,697
  Due from Amundi Pioneer Asset Management, Inc. (Amundi Pioneer),
     formerly Pioneer Investment Management, Inc.                          2,864
  Other assets                                                            30,648
--------------------------------------------------------------------------------
        Total assets                                                $290,509,557
================================================================================
LIABILITIES:
  Payables --
     Fund shares repurchased                                        $    320,431
     Distributions                                                        43,477
     Administration fee                                                   29,387
     Trustees' fees                                                          575
     Transfer agent fees                                                  81,985
     Professional fees                                                    30,567
     Printing expense                                                      6,219
  Due to affiliates                                                       33,505
  Accrued expenses and other liabilities                                  11,401
--------------------------------------------------------------------------------
        Total liabilities                                           $    557,547
================================================================================
NET ASSETS:
  Paid-in capital                                                   $289,960,827
  Distributions in excess of net investment income                       (12,608)
  Accumulated net realized gain on investments                             3,791
--------------------------------------------------------------------------------
        Net assets                                                  $289,952,010
================================================================================
NET ASSET VALUE PER SHARE:
(No par value, unlimited number of shares authorized)
  Class A (based on $225,555,228 / 225,716,993 shares)              $       1.00
  Class Y (based on $64,396,782 / 64,411,820 shares)                $       1.00
================================================================================


The accompanying notes are an integral part of these financial statements.

16 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


Statement of Operations (unaudited)

For the Six Months Ended 6/30/17



                                                                             
INVESTMENT INCOME:
  Interest                                                            $1,075,552
----------------------------------------------------------------------------------------------
        Total investment income                                                    $1,075,552
==============================================================================================
EXPENSES:
  Management fees                                                     $  527,099
  Transfer agent fees
     Class A                                                             106,930
     Class Y                                                                 135
  Shareowner communications expense                                       57,224
  Administrative expense                                                 148,065
  Custodian fees                                                          13,615
  Registration fees                                                       32,879
  Professional fees                                                       23,132
  Printing expense                                                         4,937
  Fees and expenses of nonaffiliated Trustees                              5,851
  12b-1 expense                                                          178,092
  Miscellaneous                                                           10,741
----------------------------------------------------------------------------------------------
     Total expenses                                                                $1,108,700
     Less fees waived and expenses reimbursed
        by Amundi Pioneer Asset Management, Inc.
        (Amundi Pioneer), formerly Pioneer Investment
        Management, Inc. (PIM)                                                        (58,261)
     12b-1 waiver                                                                    (178,092)
----------------------------------------------------------------------------------------------
     Net expenses                                                                  $  872,347
----------------------------------------------------------------------------------------------
        Net investment income                                                      $  203,205
----------------------------------------------------------------------------------------------
REALIZED GAIN (LOSS) ON INVESTMENTS:
  Net realized gain (loss) on investments                                          $    3,791
----------------------------------------------------------------------------------------------
  Net increase in net assets resulting from operations                             $  206,996
==============================================================================================


The accompanying notes are an integral part of these financial statements.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 17


Statements of Changes in Net Assets



----------------------------------------------------------------------------------------
                                                          Six Months
                                                          Ended
                                                          6/30/17         Year Ended
                                                          (unaudited)     12/31/16
----------------------------------------------------------------------------------------
                                                                    
FROM OPERATIONS:
Net investment income (loss)                              $     203,205   $      26,878
Net realized gain (loss) on investments                           3,791           7,604
----------------------------------------------------------------------------------------
   Net increase in net assets resulting from operations   $     206,996   $      34,482
----------------------------------------------------------------------------------------
DISTRIBUTIONS TO SHAREOWNERS:
Net investment income:
   Class A ($0.0006 and $0.0001 per share, respectively)  $    (140,716)  $     (25,421)
   Class Y ($0.0010 and $0.0001 per share, respectively)        (63,446)         (6,413)
----------------------------------------------------------------------------------------
      Total distributions to shareowners                  $    (204,162)  $     (31,834)
----------------------------------------------------------------------------------------
FROM FUND SHARE TRANSACTIONS:
Net proceeds from sale or exchange of shares              $  62,247,634   $ 170,637,865
Reinvestment of distributions                                   140,314          38,781
Cost of shares repurchased                                  (87,284,194)   (181,315,221)
----------------------------------------------------------------------------------------
   Net decrease in net assets resulting from
      Fund share transactions                             $ (24,896,246)  $ (10,638,575)
----------------------------------------------------------------------------------------
   Net decrease in net assets                             $ (24,893,412)  $ (10,635,927)
NET ASSETS:
Beginning of period                                       $ 314,845,422   $ 325,481,349
----------------------------------------------------------------------------------------
End of period                                             $ 289,952,010   $ 314,845,422
========================================================================================
Distributions in excess of net investment income          $     (12,608)  $     (11,651)
========================================================================================


The accompanying notes are an integral part of these financial statements.

18 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17




--------------------------------------------------------------------------------------
                          Six Months    Six Months
                          Ended         Ended
                          6/30/17       6/30/17          Year Ended     Year Ended
                          Shares        Amount           12/31/16       12/31/16
                          (unaudited)   (unaudited)      Shares         Amount
--------------------------------------------------------------------------------------
                                                            
Class A
Shares sold                53,811,609   $  53,811,609     151,264,180   $ 151,264,180
Reinvestment of
   distributions              139,989         139,989          38,733          38,733
Less shares repurchased   (79,541,576)    (79,541,576)   (162,090,339)   (162,090,339)
--------------------------------------------------------------------------------------
      Net decrease        (25,589,978)  $ (25,589,978)    (10,787,426)  $ (10,787,426)
======================================================================================
Class Y
Shares sold                 8,436,025   $   8,436,025      19,373,685   $  19,373,685
Reinvestment of
   distributions                  325             325              48              48
Less shares repurchased    (7,742,618)     (7,742,618)    (19,224,882)    (19,224,882)
--------------------------------------------------------------------------------------
      Net increase            693,732   $     693,732         148,851   $     148,851
======================================================================================


The accompanying notes are an integral part of these financial statements.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 19


Financial Highlights



------------------------------------------------------------------------------------------------------------------------------------
                                                  Six Months
                                                  Ended         Year           Year           Year         Year         Year
                                                  6/30/17       Ended          Ended          Ended        Ended        Ended
                                                  (unaudited)   12/31/16       12/31/15       12/31/14     12/31/13     12/31/12
------------------------------------------------------------------------------------------------------------------------------------
                                                                                                      
Class A
Net asset value, beginning of period              $   1.00      $   1.00       $   1.00       $   1.00     $   1.00     $   1.00
------------------------------------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
  Net investment income (loss)                    $  0.001(a)   $  0.000(a)(b) $  0.000(a)(b) $  0.000(b)  $  0.000(b)  $  0.000(b)
------------------------------------------------------------------------------------------------------------------------------------
Distributions to shareowners:
  Net investment income                           $ (0.001)*    $ (0.000)*(b)  $ (0.000)(b)   $ (0.000)(b) $ (0.000)(b) $ (0.000)(b)
------------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period                    $   1.00      $   1.00       $   1.00       $   1.00     $   1.00     $   1.00
====================================================================================================================================
Total return**                                        0.06%         0.01%          0.01%          0.01%        0.01%        0.01%
Ratio of net expenses to average net assets (c)       0.60%***      0.34%          0.10%          0.05%        0.08%        0.17%
Ratio of net investment income (loss) to average
  net assets                                          0.12%***      0.01%          0.01%          0.01%        0.01%        0.01%
Net assets, end of period (in thousands)          $225,555      $251,143       $261,928       $273,746     $286,961     $330,058
Ratios with no waiver of fees and assumption of
  expenses by Amundi Pioneer, formerly PIM, and
  no reduction for fees paid indirectly:
  Total expenses to average net assets (c)            0.80%***      0.82%          0.71%          0.75%        0.76%        1.30%
  Net investment income (loss) to average
     net assets                                      (0.08)%***    (0.46)%        (0.60)%        (0.69)%      (0.67)%      (1.12)%
====================================================================================================================================


*    The amount of distributions made to shareowners during the period were in
     excess of the net investment income earned by the Fund during the period. A
     portion of the accumulated net investment income was distributed to
     shareowners during the period.

**   Assumes initial investment at net asset value at the beginning of each
     period, reinvestment of all distributions, the complete redemption of the
     investment at net asset value at the end of each period and no sales
     charges. Total return would be reduced if sales charges were taken into
     account.

***  Annualized.

(a)  The per share data presented above is based on the average shares
     outstanding for the period presented.

(b)  Amount rounds to less than $0.001 or $(0.001) per share.

(c)  Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00%+, 0.00%, and 0.00%,
     respectively.

+    Amount rounds to less than 0.01%.

The accompanying notes are an integral part of these financial statements.

20 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17




------------------------------------------------------------------------------------------------------------------------------------
                                                  Six Months
                                                  Ended         Year           Year           Year         Year         Year
                                                  6/30/17       Ended          Ended          Ended        Ended        Ended
                                                  (unaudited)   12/31/16       12/31/15       12/31/14     12/31/13     12/31/12
------------------------------------------------------------------------------------------------------------------------------------
                                                                                                      
Class Y
Net asset value, beginning of period              $   1.00      $   1.00       $   1.00       $   1.00     $   1.00     $   1.00
------------------------------------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
  Net investment income (loss)                    $  0.001(a)   $  0.000(a)(b) $  0.000(a)(b) $  0.000(b)  $  0.000(b)  $  0.000(b)
------------------------------------------------------------------------------------------------------------------------------------
Distributions to shareowners:
  Net investment income                           $ (0.001)*    $ (0.000)*(b)  $ (0.000)(b)   $ (0.000)(b) $ (0.000)(b) $ (0.000)(b)
------------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period                    $   1.00      $   1.00       $   1.00       $   1.00     $   1.00     $   1.00
====================================================================================================================================
Total return**                                        0.10%         0.01%          0.01%          0.01%        0.01%        0.01%
Ratio of net expenses to average net assets (c)       0.52%***      0.34%          0.10%          0.05%        0.08%        0.13%
Ratio of net investment income (loss) to average
  net assets                                          0.20%***      0.01%          0.01%          0.01%        0.01%        0.01%
Net assets, end of period (in thousands)          $ 64,397      $ 63,703       $ 63,553       $ 58,851     $ 63,741     $ 62,578
Ratios with no waiver of fees and assumption of
  expenses by Amundi Pioneer, formerly PIM, and
  no reduction for fees paid indirectly:
  Total expenses to average net assets (c)            0.52%***      0.50%          0.46%          0.46%        0.45%        0.59%
  Net investment income (loss) to average
     net assets                                       0.20%***     (0.15)%        (0.35)%        (0.40)%      (0.36)%      (0.45)%
====================================================================================================================================


*    The amount of distributions made to shareowners during the period were in
     excess of the net investment income earned by the Fund during the period. A
     portion of the accumulated net investment income was distributed to
     shareowners during the period.

**   Assumes initial investment at net asset value at the beginning of each
     period, reinvestment of all distributions, the complete redemption of the
     investment at net asset value at the end of each period and no sales
     charges. Total return would be reduced if sales charges were taken into
     account.

***  Annualized.

(a)  The per share data presented above is based on the average shares
     outstanding for the period presented.

(b)  Amount rounds to less than $0.001 or $(0.001) per share.

(c)  Includes interest expense of 0.00%, 0.00%, 0.00%, 0.00%+, 0.00%, and 0.00%,
     respectively.

+    Amount rounds to less than 0.01%.

The accompanying notes are an integral part of these financial statements.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 21


Notes to Financial Statements | 6/30/17 (unaudited)

1. Organization and Significant Accounting Policies

Pioneer U.S. Government Money Market Fund (the Fund) is a series of Pioneer
Money Market Trust, a Delaware statutory trust. The Fund is registered under the
Investment Company Act of 1940 as a diversified, open-end management investment
company. The investment objective of the Fund is to provide high current income,
preservation of capital, and liquidity through investments in high-quality
short-term securities.

The Fund offered two classes of shares designated as Class A and Class Y shares.
Each class of shares represents an interest in the same portfolio of investments
of the Fund and has identical rights (based on relative net asset values) to
assets and liquidation proceeds. Share classes can bear different rates of
class-specific fees and expenses such as transfer agent and distribution fees.
Differences in class-specific fees and expenses will result in differences in
net investment income and, therefore, the payment of different dividends from
net investment income earned by each class. The Amended and Restated Declaration
of Trust of the Fund gives the Board of Trustees the flexibility to specify
either per-share voting or dollar-weighted voting when submitting matters for
shareowner approval. Under per-share voting, each share of a class of the Fund
is entitled to one vote. Under dollar-weighted voting, a shareowner's voting
power is determined not by the number of shares owned, but by the dollar value
of the shares on the record date. Each share class has exclusive voting rights
with respect to matters affecting only that class, including with respect to the
distribution plan for that class. There is no distribution plan for Class Y
shares.

On July 3, 2017, Amundi acquired Pioneer Investments, a group of asset
management companies located throughout the world. Amundi, one of the world's
largest asset managers, is headquartered in Paris, France. As a result of the
transaction, Pioneer Investment Management, Inc., the Fund's investment adviser,
became an indirect wholly owned subsidiary of Amundi and Amundi's wholly owned
subsidiary, Amundi USA, Inc. Prior to July 3, 2017, Pioneer Investments was
owned by Pioneer Global Asset Management S.p.A., a wholly owned subsidiary of
UniCredit S.p.A.

In connection with the transaction, the names of the Fund's investment adviser
and principal underwriter changed. Effective July 3, 2017, the name of Pioneer
Investment Management, Inc. changed to Amundi Pioneer Asset Management, Inc. and
the name of Pioneer Funds Distributor, Inc. changed to Amundi Pioneer
Distributor, Inc.

22 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


The Fund's financial statements have been prepared in conformity with U.S.
generally accepted accounting principles (U.S. GAAP) that require the management
of the Fund to make estimates and assumptions that affect the reported amounts
of assets and liabilities, the disclosure of contingent assets and liabilities
at the date of the financial statements, and the reported amounts of income,
expenses and gain or loss on investments during the reporting period. Actual
results could differ from those estimates.

The Fund is an investment company and follows investment company accounting and
reporting guidance under U.S. GAAP. The following is a summary of significant
accounting policies followed by the Fund in the preparation of its financial
statements:

A.   Security Valuation

     The net asset value of the Fund is computed once daily, on each day the New
     York Stock Exchange (NYSE) is open, as of the close of regular trading on
     the NYSE.

     Fixed income securities are valued by using prices supplied by independent
     pricing services, which consider such factors as market prices, market
     events, quotations from one or more brokers, Treasury spreads, yields,
     maturities and ratings, or may use a pricing matrix or other fair value
     methods or techniques to provide an estimated value of the security or
     instrument. A pricing matrix is a means of valuing a debt security on the
     basis of current market prices for other debt securities, historical
     trading patterns in the market for fixed income securities and/or other
     factors. Non-U.S. debt securities that are listed on an exchange will be
     valued at the bid price obtained from an independent third party pricing
     service. When independent third party pricing services are unable to supply
     prices, or when prices or market quotations are considered to be
     unreliable, the value of that security may be determined using quotations
     from one or more broker-dealers.

     Securities for which independent pricing services or broker-dealers are
     unable to supply prices or for which market prices and/or quotations are
     not readily available or are considered to be unreliable are valued by a
     fair valuation team comprised of certain personnel of Amundi Pioneer Asset
     Management, Inc. (Amundi Pioneer), formerly Pioneer Investment Management,
     Inc. (PIM), the Fund's investment adviser, pursuant to procedures adopted
     by the Fund's Board of Trustees. Amundi Pioneer's, formerly PIM's, fair
     valuation team uses fair value methods approved by the Valuation Committee
     of the Board of Trustees. Amundi Pioneer's, formerly PIM's, fair valuation
     team is responsible for monitoring developments that may impact fair valued
     securities and for discussing and assessing fair values on an ongoing
     basis, and at least quarterly, with the Valuation Committee of the Board of
     Trustees.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 23


     Shares of open-end registered investment companies (including money market
     mutual funds) are valued at such funds' net asset value. Repurchase
     agreements are valued at par. Cash may include overnight time deposits at
     approved financial institutions.

     At June 30, 2017, there were no securities valued using fair value methods
     (other than securities valued using prices supplied by independent pricing
     services).

B.   Investment Income and Transactions

     Investments purchased at a discount or premium are valued by amortizing the
     difference between the original purchase price and maturity value of the
     issue over the period to maturity. Interest income, including interest on
     income bearing cash accounts, is recorded on the accrual basis.

     Security transactions are recorded as of trade date. Gains and losses on
     sales of investments are calculated on the identified cost method for both
     financial reporting and federal income tax purposes.

C.   Federal Income Taxes

     It is the Fund's policy to comply with the requirements of the Internal
     Revenue Code applicable to regulated investment companies and to distribute
     all of its net taxable income and net realized capital gains, if any, to
     its shareowners. Therefore, no provision for federal income taxes is
     required. As of December 31, 2016, the Fund did not accrue any interest or
     penalties with respect to uncertain tax positions, which if applicable,
     would be recorded as an income tax expense in the Statement of Operations.
     Tax returns filed within the prior three years remain subject to
     examination by federal and state tax authorities.

     The amount and character of income and capital gain distributions to
     shareowners are determined in accordance with federal income tax rules,
     which may differ from U.S. GAAP. Distributions in excess of net investment
     income or net realized gains are temporary overdistributions for financial
     statement purposes resulting from differences in the recognition or
     classification of income or distributions for financial statement and tax
     purposes. Capital accounts within the financial statements are adjusted for
     permanent book/tax differences to reflect tax character, but are not
     adjusted for temporary differences.

     The tax character of current year distributions payable to shareowners will
     be determined at the end of the current taxable year.

24 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


     The tax character of current year distributions payable will be determined
     at the end of the current taxable year. The tax character of distributions
     during the year ended December 30, 2016 was as follows:



     ---------------------------------------------------------------------------
                                                                            2016
     ---------------------------------------------------------------------------
                                                                      
     Distributions paid from:
     Ordinary income                                                     $31,834
     ---------------------------------------------------------------------------
          Total                                                          $31,834
     ===========================================================================


     The following shows the components of distributable earnings (losses) on a
     federal income tax basis at December 31, 2016:



     ---------------------------------------------------------------------------
                                                                           2016
     ---------------------------------------------------------------------------
                                                                    
     Distributable earnings:
     Undistributed ordinary income                                     $  6,230
     Other book/tax temporary differences                               (17,881)
     ---------------------------------------------------------------------------
          Total                                                        $(11,651)
     ===========================================================================


D.   Fund Shares

     The Fund records sales and repurchases of its shares as of trade date. The
     Fund declares as daily dividends substantially all of its net investment
     income. All dividends are paid on a monthly basis. Short-term capital gain
     distributions, if any, may be declared with the daily dividends.

E.   Class Allocations

     Income, common expenses and realized and unrealized gains and losses are
     calculated at the Fund level and allocated daily to each class of shares
     based on its respective percentage of adjusted net assets at the beginning
     of the day.

     Distribution fees are calculated based on the average daily net asset value
     attributable to Class A shares of the Fund (see Note 4). Class Y shares do
     not pay distribution fees. All expenses and fees paid to the Fund's
     transfer agent for its services are allocated among the classes of shares
     based on the number of accounts in each class and the ratable allocation of
     related out-of-pocket expenses (see Note 3).

     Distributions to shareowners are recorded as of the ex-dividend date.
     Distributions paid by the Fund with respect to each class of shares are
     calculated in the same manner and at the same time, except that net
     investment income dividends to Class A and Class Y shares can reflect
     different transfer agent and distribution expense rates.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 25


F.   Risks

     Although the Fund seeks to preserve the value of your investment at $1.00
     per share, it cannot guarantee it will do so. It is possible to lose money
     by investing in the Fund. Fund shares are not federally insured by the
     Federal Deposit Insurance Corporation or any other government agency. The
     Fund's sponsor has no legal obligation to provide financial support to the
     Fund, and you should not expect that the sponsor will provide financial
     support at any time.

     At times, the Fund's investments may represent industries or industry
     sectors that are interrelated or have common risks, making the Fund more
     susceptible to any economic, political, or regulatory developments or other
     risks affecting those industries and industry sectors. The Fund's
     prospectus contains unaudited information regarding the Fund's principal
     risks. Please refer to that document when considering the Fund's principal
     risks.

G.   Repurchase Agreements

     Repurchase agreements are arrangements under which the Fund purchases
     securities from a broker-dealer or a bank, called the counterparty, upon
     the agreement of the counterparty to repurchase the securities from the
     Fund at a later date, and at a specific price, which is typically higher
     than the purchase price paid by the Fund. The securities purchased serve as
     the Fund's collateral for the obligation of the counterparty to repurchase
     the securities. The value of the collateral, including accrued interest, is
     required to be equal to or in excess of the repurchase price. The
     collateral for all repurchase agreements is held in safekeeping in the
     customer-only account of the Fund's custodian or a subcustodian of the
     Fund. Amundi Pioneer, formerly PIM, is responsible for determining that the
     value of the collateral remains at least equal to the repurchase price. In
     the event of a default by the counterparty, the Fund is entitled to sell
     the securities, but the Fund may not be able to sell them for the price at
     which they were purchased, thus causing a loss to the Fund. Additionally,
     if the counterparty becomes insolvent, there is some risk that the Fund
     will not have a right to the securities, or the immediate right to sell the
     securities. Open repurchase agreements as of June 30, 2017 are disclosed in
     the Fund's Schedule of Investments.

2. Management Agreement

Amundi Pioneer, formerly PIM, manages the Fund's portfolio. Management fees are
calculated daily at the annual rate of 0.35% of the Fund's average daily net
assets up to $1 billion and 0.30% on assets over $1 billion. For the six months
ended June 30, 2017, the net management fee (excluding waivers and/or
reimbursement of expenses) was equivalent to 0.35% (annualized).

26 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


Amundi Pioneer, formerly PIM, has agreed to limit the Fund's expenses for any
class of shares or waive a portion of its management fee in an effort to
maintain a net asset value of $1.00 per share. From time to time, Amundi
Pioneer, formerly PIM, and its affiliates may limit the expenses of one or more
classes for the purpose of avoiding a negative yield or increasing its yield
during the period of the limitation. These expense limitation policies are
voluntary and temporary and may be revised or terminated by Amundi Pioneer,
formerly PIM, at any time without notice. Fees waived and expenses reimbursed
during the six months ended June 30, 2017 are reflected on the Statement of
Operations.

In addition, under the management and administration agreements, certain other
services and costs, including accounting, regulatory reporting and insurance
premiums, are paid by the Fund as administrative reimbursements. Included in
"Due to affiliates" reflected on the Statement of Assets and Liabilities is
$33,505 in management fees, administrative costs and certain other
reimbursements payable to Amundi Pioneer, formerly PIM, at June 30, 2017.

3. Transfer Agent

Boston Financial Data Services serves as the transfer agent to the Fund at
negotiated rates. Transfer agent fees and payables shown on the Statement of
Operations and the Statement of Assets and Liabilities, respectively, include
sub-transfer agent expenses incurred through the Fund's omnibus relationship
contracts.

In addition, the Fund reimbursed the transfer agent for out-of-pocket expenses
incurred by the transfer agent related to shareowner communications activities
such as proxy and statement mailings and outgoing phone calls. For the six
months ended June 30, 2017, such out-of-pocket expenses by class of shares were
as follows:



--------------------------------------------------------------------------------
Shareowner Communications:
--------------------------------------------------------------------------------
                                                                      
Class A                                                                  $57,224
Class Y                                                                       --
--------------------------------------------------------------------------------
  Total                                                                  $57,224
================================================================================


4. Distribution and Service Plans

The Fund has adopted a Distribution Plan (the Plan) pursuant to Rule 12b-1 of
the Investment Company Act of 1940 with respect to its Class A shares. Pursuant
to the Plan, the Fund pays Amundi Pioneer Distributor, Inc., formerly Pioneer
Funds Distributor, Inc., 0.15% of the average daily net assets attributable to
Class A shares as compensation for personal services and/or account maintenance
services or distribution services with regard to Class A

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 27


shares. From January 1, 2017 until the six months ended June 30, 2017, the Plan
paid 0.15% (annualized) and subsequently waived the amount. Fees waived and
expenses reimbursed during the six months ended June 30, 2017 are reflected on
the Statement of Operations.

5. Results of Shareholder Meeting

At a special meeting held on June 13, 2017, shareholders of the Fund were asked
to consider the proposals described below. A report of the total votes cast by
the Fund's shareholders follows:



--------------------------------------------------------------------------------------------
                            For              Against        Abstain         Broker Non-Votes
--------------------------------------------------------------------------------------------
                                                                
Proposal 1 - To approve     144,594,002.838  8,749,157.370  7,115,864.652   25,753,695.670
a New Management
Agreement with
the Adviser




--------------------------------------------------------------------------------------------
                                                          For                 Withhold
--------------------------------------------------------------------------------------------
                                                                        
Proposal 2 - To elect Trustees
--------------------------------------------------------------------------------------------
David R. Bock                                             172,465,289.394     13,747,431.136
--------------------------------------------------------------------------------------------
Benjamin M. Friedman                                      172,001,642.296     14,211,078.234
--------------------------------------------------------------------------------------------
Margaret B.W. Graham                                      175,224,022.360     10,988,698.170
--------------------------------------------------------------------------------------------
Lisa M. Jones                                             175,568,480.825     10,644,239.705
--------------------------------------------------------------------------------------------
Lorraine H. Monchak                                       175,728,723.635     10,483,996.895
--------------------------------------------------------------------------------------------
Thomas J. Perna                                           175,025,507.804     11,187,212.726
--------------------------------------------------------------------------------------------
Marguerite A. Piret                                       173,002,679.948     13,210,040.582
--------------------------------------------------------------------------------------------
Fred J. Ricciardi                                         172,797,419.043     13,415,301.487
--------------------------------------------------------------------------------------------
Kenneth J. Taubes                                         174,862,783.913     11,349,936.617
--------------------------------------------------------------------------------------------


28 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


ADDITIONAL INFORMATION

Class R will commence operations on August 1, 2017.

Change in Independent Registered Public Accounting Firm

Prior to July 3, 2017 Pioneer Investment Management, Inc. (the "Adviser"), the
Fund's investment adviser, was an indirect, wholly owned subsidiary of UniCredit
S.p.A. ("UniCredit"). On that date, UniCredit completed the sale of its Pioneer
Investments business, which includes the Adviser, to Amundi (the "Transaction").
As a result of the Transaction, the Adviser became an indirect, wholly-owned
subsidiary of Amundi. Amundi is controlled by Credit Agricole S.A. Amundi is
headquartered in Paris, France, and, as of September 30, 2016, had more than
$1.1 trillion in assets under management worldwide.

Deloitte & Touche LLP ("D&T"), the Fund's previous independent registered public
accounting firm, informed the Audit Committee and the Board that it would no
longer be independent with respect to the Fund upon the completion of the
Transaction as a result of certain services being provided to Amundi and Credit
Agricole, and, accordingly, that it intended to resign as the Fund's independent
registered public accounting firm upon the completion of the Transaction. D&T's
resignation was effective on July 3, 2017, when the Transaction was completed.

During the periods as to which D&T has served as the Fund's independent
registered public accounting firm, including the Fund's two most recent fiscal
years preceding the fiscal year ended December 31, 2017, D&T's reports on the
Fund's financial statements have not contained an adverse opinion or disclaimer
of opinion and have not been qualified or modified as to uncertainty, audit
scope or accounting principles. Further, there have been no disagreements with
D&T on any matter of accounting principles or practices, financial statement
disclosure, or auditing scope or procedure, which, if not resolved to the
satisfaction of D&T, would have caused D&T to make reference to the subject
matter of the disagreement in connection with its report on the financial
statements. In addition, there have been no reportable events of the kind
described in Item 304(a)(1)(v) of Regulation S-K under the Securities Exchange
Act of 1934.

Effective immediately following the completion of the Transaction on July 3,
2017, the Board, acting upon the recommendation of the Audit Committee, engaged
a new independent registered public accounting firm, Ernst & Young LLP ("EY"),
for the Fund's fiscal year ended December 31, 2017.

Prior to its engagement, EY had advised the Fund's Audit Committee that EY had
identified the following matters, in each case relating to services rendered by
other member firms of Ernst & Young Global Limited, all of which are located
outside the United States, to UniCredit and certain of its subsidiaries

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 29


during the period commencing July 1, 2016, that it determined to be inconsistent
with the auditor independence rules set forth by the Securities and Exchange
Commission ("SEC"): (a) project management support services to UniCredit in the
Czech Republic, Germany, Italy, Serbia and Slovenia in relation to twenty-two
projects, that were determined to be inconsistent with Rule 2-01(c)(4)(vi) of
Regulation S-X (management functions); (b) two engagements for UniCredit in
Italy where fees were contingent/success based and that were determined to be
inconsistent with Rule 2-01(c)(5) of Regulation S-X (contingent fees); (c) four
engagements where legal and expert services were provided to UniCredit in the
Czech Republic and Germany, and twenty engagements where the legal advisory
services were provided to UniCredit in Austria, Czech Republic, Italy and
Poland, that were determined to be inconsistent with Rule 2-01(c)(4)(ix) and (x)
of Regulation S-X (legal and expert services); and (d) two engagements for
UniCredit in Italy involving assistance in the sale of certain assets, that were
determined to be inconsistent with Rule 2-01(c)(4)(viii) of Regulation S-X
(broker-dealer, investment advisor or investment banking services). None of the
foregoing services involved the Fund, any of the other funds in the Pioneer
Family of Funds or any other Pioneer entity sold by UniCredit in the
Transaction.

EY advised the Audit Committee that it had considered the matters described
above and had concluded that such matters would not impair EY's ability to
exercise objective and impartial judgment in connection with the audits of the
financial statements of the Fund under the SEC and Public Company Accounting
Oversight Board independence rules, and that a reasonable investor with
knowledge of all relevant facts and circumstances would reach the same
conclusion. Management and the Audit Committee considered these matters and
discussed the matters with EY and, based upon EY's description of the matters
and statements made by EY, Management and the Audit Committee believe that EY
will be capable of exercising objective and impartial judgment in connection
with the audits of the financial statements of the Fund, and Management further
believes that a reasonable investor with knowledge of all relevant facts and
circumstances would reach the same conclusion.

30 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


Approval of New and Interim Management Agreements

Amundi Pioneer Asset Management, Inc. (Amundi Pioneer), formerly Pioneer
Investment Management, Inc. (PIM), serves as the investment adviser to Pioneer
U.S. Government Money Market Fund (the Fund) pursuant to an investment
management agreement between Amundi Pioneer and the Fund.

On July 3, 2017, Amundi acquired Pioneer Investments, a group of asset
management companies located throughout the world (the "Transaction"). As a
result of the Transaction, Amundi Pioneer became an indirect wholly-owned
subsidiary of Amundi and Amundi's wholly-owned subsidiary, Amundi USA, Inc.
Prior to July 3, 2017, Pioneer Investments was owned by Pioneer Global Asset
Management S.p.A. ("PGAM"), a wholly-owned subsidiary of UniCredit S.p.A.
("UniCredit").

Under the Investment Company Act of 1940, the Fund's investment management
agreement with PIM (the "Current Management Agreement") terminated automatically
upon the consummation of the Transaction. In order for Amundi Pioneer to
continue to manage the Fund after the consummation of the Transaction, the
Trustees and shareholders of the Fund were required to approve a new investment
management agreement for the Fund (the "New Management Agreement"). As discussed
below, the Board of Trustees of the Fund approved the New Management Agreement
at a meeting held on March 6-7, 2017. The New Management Agreement was approved
by the shareholders of the Fund at a meeting held on June 13, 2017. The Board of
Trustees of the Fund also approved an interim investment management agreement
between Amundi Pioneer and the Fund (the "Interim Management Agreement") at the
March 6-7, 2017 meeting. The Interim Management Agreement would have taken
effect upon the closing of the Transaction in the event that the shareholders of
the Fund did not approve the New Management Agreement.

Board Evaluation of the New and Interim Management Agreements

The Board evaluated the Transaction and the New Management Agreement and Interim
Management Agreement for the Fund. In connection with their evaluation of the
Transaction and the New Management Agreement for the Fund, the Trustees
requested such information as they deemed reasonably necessary, including: (a)
the structure of the Transaction and the strategy underlying the Transaction;
(b) the anticipated benefits of the Transaction to the Fund and its
shareholders; (c) the post-Transaction plans for Amundi Pioneer, including
Amundi's plans for integration of Pioneer Investments and Amundi Pioneer with
its existing asset management businesses and plans for the future development of
Amundi Pioneer; (d) the effect of the Transaction on the ongoing services
provided to the Fund, including the need to select a

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 31


new independent registered public accounting firm for the Fund, and any plans to
modify the operations of the Fund; (e) the stability and continuity of Amundi
Pioneer's management and key employees, including compensation and benefits to
Amundi Pioneer's key employees, and retention plans and incentive plan
structure; (f) the post-Transaction indebtedness and financial resources of
Amundi Pioneer; (g) Amundi's legal and operational structure, its principal
shareholders and senior management, its investment management, risk management,
administrative, legal and compliance functions; (h) certain regulatory matters
relating to Amundi's affiliates; and (i) Amundi's commitment to the United
States, including the role of Amundi Pioneer in the larger Amundi business.

The Trustees also requested and obtained the following information in connection
with their evaluation of the Transaction and the New Management Agreement for
the Fund: (i) memoranda provided by Fund counsel that summarized the legal
standards and other considerations that are relevant to the Trustees in their
deliberations regarding the New Management Agreement; (ii) the qualifications of
the investment management teams for the Fund, as well as the level of investment
by the Fund's portfolio managers in the Fund; (iii) the Fund's management fees
and total expense ratios, the financial statements of Amundi Pioneer and its
pre- and post-Transaction parent companies, profitability analyses from Amundi
Pioneer, and analyses from Amundi Pioneer as to possible economies of scale;
(iv) the profitability of the institutional business of Amundi Pioneer and
Amundi Pioneer's affiliate, Amundi Pioneer Institutional Asset Management, Inc.
("Amundi Pioneer Institutional") as compared to that of Amundi Pioneer's fund
management business; and (v) the differences between the fees and expenses of
the Fund and the fees and expenses of Amundi Pioneer's and Amundi Pioneer
Institutional's institutional accounts, as well as the different services
provided by Adviser to the Fund and by Amundi Pioneer and Amundi Pioneer
Institutional to the institutional accounts. In addition, the Trustees
considered the information provided at regularly scheduled meetings throughout
the year regarding the Fund's performance and risk attributes, including through
meetings with investment management personnel, and took into account other
information related to the Fund provided to the Trustees at regularly scheduled
meetings. The Trustees also considered information they had received in their
review of the continuance of the Current Management Agreement for the Fund in
September 2016.

At meetings held on January 9, 2017 and January 10, 2017, the Trustees met with
representatives of Amundi and PGAM, including separate meetings of the Trustees
who are not "interested persons" of the Fund Complex ("Independent Trustees")
and counsel with representatives of Amundi and PGAM, and subsequently with
representatives of Amundi. In those meetings,

32 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


they received an extensive presentation from the representatives of Amundi,
including the chief executive officer of Amundi, describing Amundi's background
and history, its global asset management activities, the growth of its business,
and its status as the largest asset management firm in Europe and one of the
largest globally; its capital structure and financial resources, including
information as to the financing of the Transaction; its principal investors,
including its majority investor Credit Agricole S.A., and Credit Agricole's
long-term commitment to the asset management business; the philosophy and
strategy underlying the Transaction and the complementarity of Amundi's and
Pioneer Investments' respective asset management businesses; Amundi's various
operating and investment committees and how they would likely interact with
Amundi Pioneer; the proposed integration process, including the progress to date
and the establishment of various integration work streams; Amundi's plans for
management of Amundi Pioneer; Amundi's philosophy as to compensation of key
employees and its general intentions with respect to incentive plans for key
employees of Amundi Pioneer; Amundi's preliminary plans to achieve cost and
other synergies; and opportunities to further develop the business of Amundi
Pioneer and Amundi Pioneer Institutional, including in the area of institutional
asset management, and how that would benefit shareholders of the Pioneer Funds.

In those meetings, the representatives of Amundi confirmed their intention that
the Chief Executive Officer and Chief Investment Officer of Amundi Pioneer would
remain in their current positions, and confirmed that they do not currently
foresee major changes in the day-to-day investment management operations of
Amundi Pioneer with respect to the Fund as a direct result of the Transaction.
They discussed incentive arrangements for key personnel that would continue
after the closing of the Transaction and their plans to establish a new
long-term incentive plan following the closing. They also generally discussed
ways in which Amundi Pioneer could potentially draw on the expanded global
resources of Amundi post-Transaction. At those meetings, the Independent
Trustees identified certain areas to which they requested further information,
including as to trading and execution of securities transactions, research and
portfolio management and potential changes in investment process, particularly
where asset classes managed by Amundi Pioneer would overlap with asset classes
managed by Amundi, the continued availability of resources currently at Pioneer
Investments or elsewhere within Amundi to assist in management of certain Funds,
and any anticipated significant changes in operations. The Independent Trustees
considered the uncertainty as to whether the Fund's independent registered
public accounting firm could continue to act in that capacity after the closing
of the Transaction. The Independent Trustees also met with counsel to review the
information they had received to date and to discuss next steps.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 33


Subsequently, the Trustees received further information from Amundi, including
written responses to questions raised by the Independent Trustees, and received
from Amundi Pioneer the information requested of it. The Independent Trustees
reviewed the information provided with counsel at telephonic meetings held on
February 16, 2017 and February 27, 2017. The Trustees held a special in-person
Board meeting on March 6-7, 2017 for further consideration of the New Management
Agreements, the Interim Management Agreements and the Transaction. The Trustees
met again with senior executives of Amundi at the March 6-7, 2017 meeting.

At the March 6-7, 2017 meeting, based on their evaluation of the information
provided by Amundi Pioneer and Amundi, the Trustees including the Independent
Trustees voting separately, approved the New Management Agreement and the
Interim Management Agreement for the Fund. In considering the New Management
Agreement for the Fund, the Trustees considered various factors that they
determined were relevant, including the factors described below. The Trustees
did not identify any single factor as the controlling factor in their
determinations. The Trustees considered the same factors with respect to the
Interim Management Agreement for the Fund.

Nature, Extent and Quality of Services

The Trustees considered the nature, extent and quality of the services that had
been provided by Amundi Pioneer to the Fund and that are expected to be provided
by Amundi Pioneer to the Fund following the consummation of the Transaction. The
Trustees reviewed the terms of the New Management Agreement, and noted that such
terms are substantially similar to the terms of the Current Management
Agreement, except for different execution dates, effective dates and termination
dates. The Trustees reviewed Amundi Pioneer's investment approach for the Fund
and its research process. The Trustees considered the resources of Amundi
Pioneer and the personnel of Amundi Pioneer who provide investment management
services to the Fund. They also reviewed the amount of non-investment resources
and personnel of Amundi Pioneer that are involved in Amundi Pioneer's services
to the Fund, including Amundi Pioneer's compliance and legal resources and
personnel. The Trustees noted the substantial attention and high priority given
by Amundi Pioneer's senior management to the Pioneer Fund complex.

The Trustees considered that Amundi Pioneer supervises and monitors the
performance of the Fund's service providers and provides the Fund with personnel
(including Fund officers) and other resources that are necessary for the Fund's
business management and operations and that Amundi Pioneer would continue to
provide those investment management and research services and resources to the
Fund following the consummation of the Transaction. The Trustees also considered
that, as administrator, Amundi

34 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


Pioneer would continue to be responsible for the administration of the Fund's
business and other affairs. The Trustees considered the fees to be paid to
Amundi Pioneer for the provision of administration services.

The Trustees considered that Deloitte & Touche LLP informed the Board that it
would no longer be independent with respect to the Fund upon the completion of
the Transaction and, accordingly, that it would be necessary for the Board to
engage a new independent registered public accounting firm for the Fund.

The Trustees considered that the Transaction was not expected to have a material
adverse impact on the nature, scope and overall quality of services provided to
the Fund and its shareholders, including investment management, risk management,
administrative, compliance, legal and other services, as a result of the
Transaction.

In that regard, the Trustees considered that Amundi is one of the largest asset
managers globally, and that Amundi Pioneer may have access to additional
research and portfolio management capabilities as a result of the Transaction
and that Amundi Pioneer, as part of Amundi, is expected to have an enhanced
global presence that may contribute to an increase in the overall scale and
resources of Amundi Pioneer. Furthermore, in considering whether the Transaction
would be expected to have a material adverse impact on the nature, scope and
overall quality of services provided to the Fund and its shareholders, the
Trustees considered the statements by representatives of Amundi that they expect
the Chief Executive Officer and Chief Investment Officer of Amundi Pioneer to
remain in their current positions and that they do not currently foresee major
changes in the day-to-day investment management operations of Amundi Pioneer as
a direct result of the Transaction, or the risk management, legal or compliance
services provided by Amundi Pioneer, with respect to the Fund. They further
considered the current incentive arrangements for key personnel of Amundi
Pioneer that would continue after the closing of the Transaction. They also
noted Amundi's stated intention to establish a new long-term incentive plan
following the closing.

The Trustees also took into account their experience in evaluating the proposed
combination of Pioneer Investments and Santander Asset Management, which was
announced in September, 2014 and abandoned in July, 2016. In light of, among
other things, this experience, the Trustees determined that they were not able
to identify any realistic alternatives to approving the New Management Agreement
that would provide the level of services to the Fund and its shareholders that
are expected to be provided by Amundi Pioneer after the closing of the
Transaction.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 35


Based on these considerations, the Trustees concluded that the nature, extent
and quality of services that Amundi Pioneer would continue to provide to the
Fund under the New Management Agreement would be satisfactory and consistent
with the terms of the New Management Agreement.

Performance of the Fund

In considering the Fund's performance, the Trustees regularly reviewed and
discussed throughout the year data prepared by Amundi Pioneer and information
comparing the Fund's performance with the performance of its peer group of
funds, as classified by each of Morningstar, Inc. (Morningstar) and Lipper, and
the performance of the Fund's benchmark index. They also discussed the Fund's
performance with Amundi Pioneer on a regular basis.

The Trustees' regular reviews and discussions were factored into the Trustees'
deliberations concerning the approval of the New Management Agreement.

Management Fee and Expenses

The Trustees noted that the stated management fees to be paid by the Fund are
identical under the Current Management Agreement and the New Management
Agreement. The Trustees considered information showing the fees and expenses of
the Fund in comparison to the management fees and expense ratios of its peer
group of funds as classified by Morningstar and also to the expense ratios of a
peer group of funds selected on the basis of criteria determined by the
Independent Trustees for this purpose using data provided by Strategic Insight
Mutual Fund Research and Consulting, LLC (Strategic Insight), an independent
third party. In all quintile rankings referred to below, first quintile is most
favorable to the Fund's shareowners. To the extent applicable, the Trustees also
considered the impact of transfer agency, sub-transfer agency, and other
non-management fee expenses on the expense ratios of the Fund. The Trustees
noted that they separately review the Fund's transfer agency, sub-transfer
agency and intermediary arrangements and that the results of the most recent
such review were considered in the consideration of the Fund's expense ratio.

The Trustees considered that the Fund's management fee as of September 30, 2016
was in the fourth quintile relative to the management fees paid by other funds
in its Morningstar category for the comparable period. The Trustees considered
that the Fund's management fee was approximately four basis points higher than
the median management fee paid by other funds in its Morningstar category. The
Trustees also considered the breakpoint in the management fee schedule and the
reduced fee rate above a certain asset level. The Trustees considered that the
expense ratio of the Fund's Class A shares as of September 30, 2016 was in the
first quintile relative to its Morningstar category and in the first quintile
relative to its Strategic Insight peer group, in

36 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


each case for the comparable period. The Trustees noted that Amundi Pioneer was
waiving fees and/or reimbursing expenses in order to limit the ordinary
operating expenses of the Fund and maintain a positive yield.

The Trustees reviewed management fees charged by Amundi Pioneer and Amundi
Pioneer Institutional to institutional and other clients, including publicly
offered European funds sponsored by Amundi Pioneer's affiliates, unaffiliated
U.S. registered investment companies (in a sub-advisory capacity), and
unaffiliated foreign and domestic separate accounts. The Trustees also
considered Amundi Pioneer's costs in providing services to the Fund and Amundi
Pioneer's and Amundi Pioneer Institutional's costs in providing services to the
other clients and considered the differences in management fees and profit
margins for fund and non-fund services. In evaluating the fees associated with
Amundi Pioneer's and Amundi Pioneer Institutional's client accounts, the
Trustees took into account the respective demands, resources and complexity
associated with the Fund and other client accounts. The Trustees noted that in
some instances the fee rates for those clients were lower than the management
fee for the Fund and considered that, under both the Current Management
Agreement and the New Management Agreement, Amundi Pioneer would perform
additional services for the Fund that it does not provide to those other clients
or services that are broader in scope, including oversight of the Fund's other
service providers and activities related to compliance and the extensive
regulatory and tax regimes to which the Fund is subject. The Trustees also
considered the different risks associated with Amundi Pioneer's management of
the Fund and Amundi Pioneer's and Amundi Pioneer Institutional's management of
the other client accounts.

The Trustees concluded that the management fee payable by the Fund to Amundi
Pioneer was reasonable in relation to the nature and quality of the services to
be provided by Amundi Pioneer.

Profitability

The Trustees considered information provided by Amundi Pioneer regarding the
profitability of Amundi Pioneer with respect to the advisory services provided
by Amundi Pioneer to the Fund, including the methodology used by Amundi Pioneer
in allocating certain of its costs to the management of the Fund. The Trustees
also considered Amundi Pioneer's profit margin in connection with the overall
operation of the Fund. They further reviewed the financial results, including
the profit margins, realized by Amundi Pioneer and Amundi Pioneer Institutional
from non-fund businesses. The Trustees considered Amundi Pioneer's profit
margins with respect to the Fund in comparison to the limited industry data
available and noted that the profitability of any adviser was affected by
numerous factors, including its

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 37


organizational structure and method for allocating expenses. The Trustees
concluded that Amundi Pioneer's profitability with respect to the management of
the Fund was not unreasonable.

Economies of Scale

The Trustees considered Amundi Pioneer's views relating to economies of scale in
connection with the Pioneer Funds as fund assets grow and the extent to which
any such economies of scale are shared with the Fund and Fund shareholders. The
Trustees recognize that economies of scale are difficult to identify and
quantify, and that, among other factors that may be relevant, are the following:
fee levels, expense subsidization, investment by Amundi Pioneer in research and
analytical capabilities and Amundi Pioneer's commitment and resource allocation
to the Fund. The Trustees noted that profitability also may be an indicator of
the availability of any economies of scale, although profitability may vary for
other reasons including due to reductions in expenses. The Trustees concluded
that economies of scale, if any, were being appropriately shared with the Fund.

Other Benefits

The Trustees considered the other benefits that Amundi Pioneer enjoys from its
relationship with the Fund. The Trustees considered the character and amount of
fees paid or to be paid by the Fund, other than under the Current Management
Agreement or the New Management Agreement, for services provided by Amundi
Pioneer and its affiliates. The Trustees further considered the revenues and
profitability of Amundi Pioneer's businesses other than the Fund business. To
the extent applicable, the Trustees also considered the benefits to the Fund and
to Amundi Pioneer and its affiliates from the use of "soft" commission dollars
generated by the Fund to pay for research and brokerage services.

The Trustees considered that following the completion of the Transaction, Amundi
Pioneer will be the principal U.S. asset management business of Amundi, and that
Amundi's worldwide asset management business will manage over $1.38 trillion in
assets (including the Pioneer Funds). This may create opportunities for Amundi
Pioneer, Amundi Pioneer Institutional and Amundi that derive from Amundi
Pioneer's relationships with the Fund, including Amundi's ability to market the
services of Amundi Pioneer globally. The Trustees noted that Amundi Pioneer may
have access to additional research capabilities as a result of the Transaction
and Amundi's enhanced global presence that may contribute to an increase of the
overall scale of Amundi Pioneer. The Trustees considered that Amundi Pioneer and
the Fund are expected to receive reciprocal intangible benefits from the
relationship, including mutual brand recognition and, for the Fund, direct and
indirect

38 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


access to the resources of a large global asset manager. The Trustees concluded
that any such benefits received by Amundi Pioneer as a result of its
relationship with the Fund were reasonable.

Conclusion

After consideration of the factors described above as well as other factors, the
Trustees, including the Independent Trustees, concluded that the New Management
Agreement and the Interim Management Agreement for the Fund, including the fees
payable thereunder, were fair and reasonable and voted to approve the New
Management Agreement and the Interim Management Agreement, and to recommend that
shareholders approve the New Management Agreement.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 39


Trustees, Officers and Service Providers

Trustees                                    Officers
Thomas J. Perna, Chairman                   Lisa M. Jones, President and Chief
David R. Bock                                 Executive Officer
Benjamin M. Friedman                        Mark E. Bradley, Treasurer and
Margaret B.W. Graham                          Chief Financial Officer
Lisa M. Jones                               Christopher J. Kelley, Secretary and
Lorraine H. Monchak                           Chief Legal Officer
Marguerite A. Piret
Fred J. Ricciardi
Kenneth J. Taubes

Investment Adviser and Administrator
Amundi Pioneer Asset Management, Inc., formerly
Pioneer Investment Management, Inc.

Custodian and Sub-Administrator
Brown Brothers Harriman & Co.

Principal Underwriter
Amundi Pioneer Distributor, Inc., formerly
Pioneer Funds Distributor, Inc.

Legal Counsel
Morgan, Lewis & Bockius LLP

Shareowner Services and Transfer Agent
Boston Financial Data Services, Inc.

Proxy Voting Policies and Procedures of the Fund are available without charge,
upon request, by calling our toll free number (1-800-225-6292). Information
regarding how the Fund voted proxies relating to portfolio securities during the
most recent 12-month period ended June 30 is publicly available to shareowners
at www.amundipioneer.com. This information is also available on the Securities
and Exchange Commission's web site at www.sec.gov.

40 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


                          This page is for your notes.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 41


                          This page is for your notes.

42 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


                          This page is for your notes.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17 43


                          This page is for your notes.

44 Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/17


How to Contact Amundi Pioneer

We are pleased to offer a variety of convenient ways for you to contact us for
assistance or information.

Call us for:
--------------------------------------------------------------------------------
Account Information, including existing accounts,
new accounts, prospectuses, applications
and service forms                                                 1-800-225-6292

FactFone(SM) for automated fund yields, prices,
account information and transactions                              1-800-225-4321

Retirement plans information                                      1-800-622-0176

Write to us:
--------------------------------------------------------------------------------
Amundi Pioneer
P.O. Box 55014
Boston, Massachusetts 02205-5014

Our toll-free fax                                                 1-800-225-4240

Our internet e-mail address                  ask.amundipioneer@amundipioneer.com
(for general questions about Amundi Pioneer only)

Visit our web site: www.amundipioneer.com

This report must be preceded or accompanied by a prospectus. The Fund files a
complete schedule of investments with the Securities and Exchange Commission for
the first and third quarters for each fiscal year on Form N-Q. Shareholders may
view the filed Form N-Q by visiting the Commission's web site at
http://www.sec.gov. The filed form may also be viewed and copied at the
Commission's Public Reference Room in Washington, DC. Information regarding the
operations of the Public Reference Room may be obtained by calling
1-800-SEC-0330.


[LOGO]   Amundi Pioneer
         ==============
       ASSET MANAGEMENT

Amundi Pioneer Asset Management, Inc.
60 State Street
Boston, MA 02109
www.amundipioneer.com

Securities offered through Amundi Pioneer Funds Distributor, Inc.
60 State Street, Boston, MA 02109
Underwriter of Pioneer Mutual Funds, Member SIPC
(C) 2017 Amundi Pioneer Asset Management 19399-11-0817



ITEM 2. CODE OF ETHICS.

(a) Disclose whether, as of the end of the period covered by the report, the
registrant has adopted a code of ethics that applies to the registrant's
principal executive officer, principal financial officer, principal accounting
officer or controller, or persons performing similar functions, regardless of
whether these individuals are employed by the registrant or a third party.  If
the registrant has not adopted such a code of ethics, explain why it has not
done so.

The registrant has adopted, as of the end of the period covered by this report,
a code of ethics that applies to the registrant's principal executive officer,
principal financial officer, principal accounting officer and controller.

(b) For purposes of this Item, the term "code of ethics" means written standards
that are reasonably designed to deter wrongdoing and to promote:

        (1) Honest and ethical conduct, including the ethical handling of actual
        or apparent conflicts of interest between personal and professional
        relationships;

        (2) Full, fair, accurate, timely, and understandable disclosure in
        reports and documents that a registrant files with, or submits to, the
        Commission and in other public communications made by the registrant;

        (3) Compliance with applicable governmental laws, rules, and
        regulations;

        (4) The prompt internal reporting of violations of the code to an
        appropriate person or persons identified in the code; and

        (5) Accountability for adherence to the code.

(c) The registrant must briefly describe the nature of any amendment, during the
period covered by the report, to a provision of its code of ethics that applies
to the registrant's principal executive officer, principal financial officer,
principal accounting officer or controller, or persons performing similar
functions, regardless of whether these individuals are employed by the
registrant or a third party, and that relates to any element of the code of
ethics definition enumerated in paragraph (b) of this Item. The registrant must
file a copy of any such amendment as an exhibit pursuant to Item 10(a), unless
the registrant has elected to satisfy paragraph (f) of this Item by posting its
code of ethics on its website pursuant to paragraph (f)(2) of this Item, or by
undertaking to provide its code of ethics to any person without charge, upon
request, pursuant to paragraph (f)(3) of this Item.

The registrant has made no amendments to the code of ethics during the period
covered by this report.

(d) If the registrant has, during the period covered by the report, granted a
waiver, including an implicit waiver, from a provision of the code of ethics to
the registrant's principal executive officer, principal financial officer,
principal accounting officer or controller, or persons performing similar
functions, regardless of whether these individuals are employed by the
registrant or a third party, that relates to one or more of the items set forth
in paragraph (b) of this Item, the registrant must briefly describe the nature
of the waiver, the name of the person to whom the waiver was granted, and the
date of the waiver.

Not applicable.

(e) If the registrant intends to satisfy the disclosure requirement under
paragraph (c) or (d) of this Item regarding an amendment to, or a waiver from,
a provision of its code of ethics that applies to the registrant's principal
executive officer, principal financial officer, principal accounting officer or
controller, or persons performing similar functions and that relates to any
element of the code of ethics definition enumerated in paragraph (b) of this
Item by posting such information on its Internet website, disclose the
registrant's Internet address and such intention.

Not applicable.

(f) The registrant must:

        (1) File with the Commission, pursuant to Item 12(a)(1), a copy of
        its code of ethics that applies to the registrant's principal
        executive officer,principal financial officer, principal accounting
        officer or controller, or persons performing similar functions,
        as an exhibit to its annual
        report on this Form N-CSR (see attachment);

        (2) Post the text of such code of ethics on its Internet website and
        disclose, in its most recent report on this Form N-CSR, its Internet
        address and the fact that it has posted such code of ethics on its
        Internet website; or

        (3) Undertake in its most recent report on this Form N-CSR to provide to
        any person without charge, upon request, a copy of such code of ethics
        and explain the manner in which such request may be made.
	See Item 10(2)

ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT.

(a) (1)  Disclose that the registrant's board of trustees has determined that
         the registrant either:

    (i)  Has at least one audit committee financial expert serving on its audit
         committee; or

    (ii) Does not have an audit committee financial expert serving on its audit
         committee.

The registrant's Board of Trustees has determined that the registrant has at
least one audit committee financial expert.

    (2) If the registrant provides the disclosure required by paragraph
(a)(1)(i) of this Item, it must disclose the name of the audit committee
financial expert and whether that person is "independent." In order to be
considered "independent" for purposes of this Item, a member of an audit
committee may not, other than in his or her capacity as a member of the audit
committee, the board of trustees, or any other board committee:

    (i)  Accept directly or indirectly any consulting, advisory, or other
         compensatory fee from the issuer; or

    (ii) Be an "interested person" of the investment company as defined in
         Section 2(a)(19) of the Act (15 U.S.C. 80a-2(a)(19)).

Ms. Marguerite A. Piret, an independent trustee, is such an audit committee
financial expert.

    (3) If the registrant provides the disclosure required by paragraph (a)(1)
(ii) of this Item, it must explain why it does not have an audit committee
financial expert.

Not applicable.


ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES.

(a) Disclose, under the caption AUDIT FEES, the aggregate fees billed for each
of the last two fiscal years for professional services rendered by the principal
accountant for the audit of the registrant's annual financial statements or
services that are normally provided by the accountant in connection with
statutory and regulatory filings or engagements for those fiscal years.

N/A

(b) Disclose, under the caption AUDIT-RELATED FEES, the aggregate fees billed in
each of the last two fiscal years for assurance and related services by the
principal accountant that are reasonably related to the performance of the audit
of the registrant's financial statements and are not reported under
paragraph (a) of this Item. Registrants shall describe the nature of the
services comprising the fees disclosed under this category.

N/A


(c) Disclose, under the caption TAX FEES, the aggregate fees billed in each of
the last two fiscal years for professional services rendered by the principal
accountant for tax compliance, tax advice, and tax planning. Registrants shall
describe the nature of the services comprising the fees disclosed under this
category.

N/A

(d) Disclose, under the caption ALL OTHER FEES, the aggregate fees billed in
each of the last two fiscal years for products and services provided by the
principal accountant, other than the services reported in paragraphs (a) through
(c) of this Item. Registrants shall describe the nature of the services
comprising the fees disclosed under this category.

N/A

(e) (1) Disclose the audit committee's pre-approval policies and procedures
described in paragraph (c)(7) of Rule 2-01 of Regulation S-X.

 PIONEER FUNDS
            APPROVAL OF AUDIT, AUDIT-RELATED, TAX AND OTHER SERVICES
                       PROVIDED BY THE INDEPENDENT AUDITOR

                  SECTION I - POLICY PURPOSE AND APPLICABILITY

The Pioneer Funds recognize the importance of maintaining the independence of
their outside auditors. Maintaining independence is a shared responsibility
involving Pioneer Investment Management, Inc ("PIM"), the audit committee and
the independent auditors.

The Funds recognize that a Fund's independent auditors: 1) possess knowledge of
the Funds, 2) are able to incorporate certain services into the scope of the
audit, thereby avoiding redundant work, cost and disruption of Fund personnel
and processes, and 3) have expertise that has value to the Funds. As a result,
there are situations where it is desirable to use the Fund's independent
auditors for services in addition to the annual audit and where the potential
for conflicts of interests are minimal. Consequently, this policy, which is
intended to comply with Rule 210.2-01(C)(7), sets forth guidelines and
procedures to be followed by the Funds when retaining the independent audit firm
to perform audit, audit-related tax and other services under those
circumstances, while also maintaining independence.

Approval of a service in accordance with this policy for a Fund shall also
constitute approval for any other Fund whose pre-approval is required pursuant
to Rule 210.2-01(c)(7)(ii).

In addition to the procedures set forth in this policy, any non-audit services
that may be provided consistently with Rule 210.2-01 may be approved by the
Audit Committee itself and any pre-approval that may be waived in accordance
with Rule 210.2-01(c)(7)(i)(C) is hereby waived.

Selection of a Fund's independent auditors and their compensation shall be
determined by the Audit Committee and shall not be subject to this policy.



                               SECTION II - POLICY

---------------- -------------------------------- -------------------------------------------------
SERVICE           SERVICE CATEGORY DESCRIPTION      SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES
CATEGORY
---------------- -------------------------------- -------------------------------------------------
                                            
I.  AUDIT        Services that are directly       o Accounting research assistance
SERVICES         related to performing the        o SEC consultation, registration
                 independent audit of the Funds     statements, and reporting
                                                  o Tax accrual related matters
                                                  o Implementation of new accounting
                                                    standards
                                                  o Compliance letters (e.g. rating agency
                                                    letters)
                                                  o Regulatory reviews and assistance
                                                    regarding financial matters
                                                  o Semi-annual reviews (if requested)
                                                  o Comfort letters for closed end
                                                    offerings
---------------- -------------------------------- -------------------------------------------------
II.              Services which are not           o AICPA attest and agreed-upon procedures
AUDIT-RELATED    prohibited under Rule            o Technology control assessments
SERVICES         210.2-01(C)(4) (the "Rule")      o Financial reporting control assessments
                 and are related extensions of    o Enterprise security architecture
                 the audit services support the     assessment
                 audit, or use the
                 knowledge/expertise gained
                 from the audit procedures as a
                 foundation to complete the
                 project.  In most cases, if
                 the Audit-Related Services are
                 not performed by the Audit
                 firm, the scope of the Audit
                 Services would likely
                 increase.  The Services are
                 typically well-defined and
                 governed by accounting
                 professional standards (AICPA,
                 SEC, etc.)
---------------- -------------------------------- -------------------------------------------------

 ------------------------------------- ------------------------------------
                                    
   AUDIT COMMITTEE APPROVAL POLICY               AUDIT COMMITTEE
                                                REPORTING POLICY
 ------------------------------------- ------------------------------------
                                    
 o "One-time" pre-approval             o A summary of all such
   for the audit period for all          services and related fees
   pre-approved specific service         reported at each regularly
   subcategories.  Approval of the       scheduled Audit Committee
   independent auditors as               meeting.
   auditors for a Fund shall
   constitute pre approval for
   these services.
 ------------------------------------- ------------------------------------
 o "One-time" pre-approval             o A summary of all such
   for the fund fiscal year within       services and related fees
   a specified dollar limit              (including comparison to
   for all pre-approved                  specified dollar limits)
   specific service subcategories        reported quarterly.

 o Specific approval is
   needed to exceed the
   pre-approved dollar limit for
   these services (see general
   Audit Committee approval policy
   below for details on obtaining
   specific approvals)

 o Specific approval is
   needed to use the Fund's
   auditors for Audit-Related
   Services not denoted as
   "pre-approved", or
   to add a specific service
   subcategory as "pre-approved"
 ------------------------------------- ------------------------------------




                     SECTION III - POLICY DETAIL, CONTINUED

----------------------- --------------------------- -----------------------------------------------
   SERVICE CATEGORY          SERVICE CATEGORY        SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES
                               DESCRIPTION
----------------------- --------------------------- -----------------------------------------------
                                              
III. TAX SERVICES       Services which are not      o Tax planning and support
                        prohibited by the Rule,     o Tax controversy assistance
                        if an officer of the Fund   o Tax compliance, tax returns, excise
                        determines that using the     tax returns and support
                        Fund's auditor to provide   o Tax opinions
                        these services creates
                        significant synergy in
                        the form of efficiency,
                        minimized disruption, or
                        the ability to maintain a
                        desired level of
                        confidentiality.
----------------------- --------------------------- -----------------------------------------------

------------------------------------- -------------------------
  AUDIT COMMITTEE APPROVAL POLICY         AUDIT COMMITTEE
                                          REPORTING POLICY
------------------------------------- -------------------------
------------------------------------- -------------------------
o "One-time" pre-approval             o A summary of
  for the fund fiscal  year             all such services and
  within a specified dollar limit       related fees
  				        (including comparison
  			                to specified dollar
  			                limits) reported
  			                quarterly.

o Specific approval is
  needed to exceed the
  pre-approved dollar limits for
  these services (see general
  Audit Committee approval policy
  below for details on obtaining
  specific approvals)

o Specific approval is
  needed to use the Fund's
  auditors for tax services not
  denoted as pre-approved, or to add a specific
  service subcategory as
  "pre-approved"
------------------------------------- -------------------------




                     SECTION III - POLICY DETAIL, CONTINUED

----------------------- --------------------------- -----------------------------------------------
   SERVICE CATEGORY          SERVICE CATEGORY        SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES
                               DESCRIPTION
----------------------- --------------------------- -----------------------------------------------
                                              
IV.  OTHER SERVICES     Services which are not      o Business Risk Management support
                        prohibited by the Rule,     o Other control and regulatory
A. SYNERGISTIC,         if an officer of the Fund     compliance projects
UNIQUE QUALIFICATIONS   determines that using the
                        Fund's auditor to provide
                        these services creates
                        significant synergy in
                        the form of efficiency,
                        minimized disruption,
                        the ability to maintain a
                        desired level of
                        confidentiality, or where
                        the Fund's auditors
                        posses unique or superior
                        qualifications to provide
                        these services, resulting
                        in superior value and
                        results for the Fund.
----------------------- --------------------------- -----------------------------------------------

--------------------------------------- ------------------------
    AUDIT COMMITTEE APPROVAL POLICY         AUDIT COMMITTEE
                                            REPORTING POLICY
------------------------------------- --------------------------
                                   
o "One-time" pre-approval             o A summary of
  for the fund fiscal year within       all such services and
  a specified dollar limit              related fees
  			               (including comparison
  			                to specified dollar
  				        limits) reported
                                        quarterly.
o Specific approval is
  needed to exceed the
  pre-approved dollar limits for
  these services (see general
  Audit Committee approval policy
  below for details on obtaining
  specific approvals)

o Specific approval is
  needed to use the Fund's
  auditors for "Synergistic" or
  "Unique Qualifications" Other
  Services not denoted as
  pre-approved to the left, or to
  add a specific service
  subcategory as "pre-approved"
------------------------------------- --------------------------




                     SECTION III - POLICY DETAIL, CONTINUED

----------------------- ------------------------- -----------------------------------------------
   SERVICE CATEGORY         SERVICE CATEGORY        SPECIFIC PROHIBITED SERVICE SUBCATEGORIES
                              DESCRIPTION
----------------------- ------------------------- -----------------------------------------------
                                            
PROHIBITED  SERVICES    Services which result     1. Bookkeeping or other services
                        in the auditors losing       related to the accounting records or
                        independence status          financial statements of the audit
                        under the Rule.              client*
                                                  2. Financial information systems design
                                                     and implementation*
                                                  3. Appraisal or valuation services,
                                                     fairness* opinions, or
                                                     contribution-in-kind reports
                                                  4. Actuarial services (i.e., setting
                                                     actuarial reserves versus actuarial
                                                     audit work)*
                                                  5. Internal audit outsourcing services*
                                                  6. Management functions or human
                                                     resources
                                                  7. Broker or dealer, investment
                                                     advisor, or investment banking services
                                                  8. Legal services and expert services
                                                     unrelated to the audit
                                                  9. Any other service that the Public
                                                     Company Accounting Oversight Board
                                                     determines, by regulation, is
                                                     impermissible
----------------------- ------------------------- -----------------------------------------------

------------------------------------------- ------------------------------
     AUDIT COMMITTEE APPROVAL POLICY               AUDIT COMMITTEE
                                                  REPORTING POLICY
------------------------------------------- ------------------------------
o These services are not to be              o A summary of all
  performed with the exception of the(*)      services and related
  services that may be permitted              fees reported at each
  if they would not be subject to audit       regularly scheduled
  procedures at the audit client (as          Audit Committee meeting
  defined in rule 2-01(f)(4)) level           will serve as continual
  the firm providing the service.             confirmation that has
  				              not provided any
                                              restricted services.
------------------------------------------- ------------------------------

--------------------------------------------------------------------------------
GENERAL AUDIT COMMITTEE APPROVAL POLICY:
o For all projects, the officers of the Funds and the Fund's auditors will each
  make an assessment to determine that any proposed projects will not impair
  independence.

o Potential services will be classified into the four non-restricted service
  categories and the "Approval of Audit, Audit-Related, Tax and Other
  Services" Policy above will be applied. Any services outside the specific
  pre-approved service subcategories set forth above must be specifically
  approved by the Audit Committee.

o At least quarterly, the Audit Committee shall review a report summarizing the
  services by service category, including fees, provided by the Audit firm as
  set forth in the above policy.

--------------------------------------------------------------------------------


    (2) Disclose the percentage of services described in each of paragraphs (b)
   through (d) of this Item that were approved by the audit committee pursuant
   to paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X.

N/A

(f) If greater than 50 percent, disclose the percentage of hours expended on the
principal accountants engagement to audit the registrant's financial statements
for the most recent fiscal year that were attributed to work performed by
persons other than the principal accountant's full-time, permanent employees.

N/A

(g) Disclose the aggregate non-audit fees billed by the registrants accountant
for services rendered to the registrant, and rendered to the registrants
investment adviser (not including any sub-adviser whose role is primarily
portfolio management and is subcontracted with or overseen by another investment
adviser), and any entity controlling, controlled by, or under common control
with the adviser that provides ongoing services to the registrant for each of
the last two fiscal years of the registrant.

N/A

(h) Disclose whether the registrants audit committee of the board of trustees
has considered whether the provision of non-audit services that were rendered to
the registrants investment adviser (not including any subadviser whose role is
primarily portfolio management and is subcontracted with or overseen by another
investment adviser), and any entity controlling, controlled by, or under common
control with the investment adviser that provides ongoing services to the
registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of
Rule 2-01 of Regulation S-X is compatible with maintaining the principal
accountant's independence.

The Fund's audit committee of the Board of Trustees
has considered whether the provision of non-audit
services that were rendered to the Affiliates (as
defined) that were not pre- approved pursuant to
paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is
compatible with maintaining the principal accountant's
independence.

ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS

(a) If the registrant is a listed issuer as defined in Rule 10A-3
under the Exchange Act (17 CFR 240.10A-3), state whether
or not the registrant has a separately-designated standing
 audit committee established in accordance with Section
3(a)(58)(A) of the Exchange Act (15 U.S.C. 78c(a)(58)(A)).
If the registrant has such a committee, however designated,
identify each committee member. If the entire board of directors
is acting as the registrant's audit committee as specified in
Section 3(a)(58)(B) of the Exchange Act (15 U.S.C. 78c(a)(58)(B)),
so state.

N/A

(b) If applicable, provide the disclosure required by Rule 10A-3(d)
under the Exchange Act (17 CFR 240.10A-3(d)) regarding an exemption
from the listing standards for audit committees.

N/A

ITEM 6. SCHEDULE OF INVESTMENTS.

File Schedule of Investments in securities of unaffiliated issuers
as of the close of the reporting period as set forth in 210.1212
of Regulation S-X [17 CFR 210.12-12], unless the schedule is
included as part of the report to shareholders filed under Item
1 of this Form.

Included in Item 1


ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR
CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

A closed-end management investment company that is filing an annual report on
this Form N-CSR must, unless it invests exclusively in non-voting securities,
describe the policies and procedures that it uses to determine how to vote
proxies relating to portfolio securities, including the procedures that the
company uses when a vote presents a conflict between the interests of its
shareholders, on the one hand, and those of the company's investment adviser;
principal underwriter; or any affiliated person (as defined in Section 2(a)(3)
of the Investment Company Act of 1940 (15 U.S.C. 80a-2(a)(3)) and the rules
thereunder) of the company, its investment adviser, or its principal
underwriter, on the other. Include any policies and procedures of the company's
investment adviser, or any other third party, that the company uses, or that are
used on the company's behalf, to determine how to vote proxies relating to
portfolio securities.

Not applicable to open-end management investment companies.



ITEM 8. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

(a) If the registrant is a closed-end management investment company that
is filing an annual report on this Form N-CSR,provide the following
information:
(1) State the name, title, and length of service of the person or persons
employed by or associated with the registrant or an investment adviser
of the registrant who are primarily responsible for the day-to-day management
of the registrant's portfolio ("Portfolio Manager"). Also state each Portfolio
Manager's business experience during the past 5 years.


Not applicable to open-end management investment companies.


ITEM 9. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT
INVESTMENT COMPANY AND AFFILIATED PURCHASERS.

(a) If the registrant is a closed-end management investment company,
in the following tabular format, provide the information specified in
paragraph (b) of this Item with respect to any purchase made by or on
behalf of the registrant or any affiliated purchaser, as defined in
Rule 10b-18(a)(3) under the Exchange Act (17 CFR 240.10b-18(a)(3)), of
shares or other units of any class of the registrant's equity securities
that is registered by the registrant pursuant to Section 12 of the
Exchange Act (15 U.S.C. 781).

Not applicable to open-end management investment companies.


ITEM 10. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

Describe any material changes to the procedures by which shareholders
may recommend nominees to the registrant's board of directors, where
those changes were implemented after the registrant last provided
disclosure in response to the requirements of Item 407(c)(2)(iv) of
Regulation S-R(17 CFR 229.407)(as required by Item 22(b)(15))
of Schedule 14A (17 CFR 240.14a-101), or this Item.


There have been no material changes to the procedures by which the
shareholders may recommend nominees to the registrant's board of
directors since the registrant last provided disclosure in response
to the requirements of Item 407(c)(2)(iv) of Regulation S-R of Schedule 14(A)
in its definitive proxy statement, or this item.


ITEM 11. CONTROLS AND PROCEDURES.

(a) Disclose the conclusions of the registrant's principal executive and
principal financials officers, or persons performing similar functions,
regarding the effectiveness of the registrant's disclosure
controls and procedures (as defined in Rule 30a-3(c) under the Act (17 CFR
270.30a-3(c))) as of a date within 90 days of the filing date of the report
that includes the disclosure required by this paragraph,
based on the evaluation of these controls and procedures required by Rule
30a-3(b) under the Act (17 CFR 270.30(a)-3(b) and Rules 13a-15(b) or 15d-15(b)
under the Exchange Act (17 CFR 240.13a-15(b) or 240.15d-15(b)).

The registrant's principal executive officer
and principal financial officer have
concluded that the registrant's disclosure
controls and procedures are effective based
on the evaluation of these controls and
procedures as of a date within 90 days of the
filing date of this report.


(b) Disclose any change in the registrant's internal control over financial
reporting (as defined in Rule 30a-3(d) under the Act (17CFR 270.30a-3(d)) that
occured during the second fiscal quarter of the period covered by this report
that has materially affected, or is reasonably likely to materially affect,
the registrant's internal control over financial reporting.

There were no significant changes in the
registrant's internal control over financial
reporting that occurred during the second
fiscal quarter of the period covered by this
report that have materially affected, or are
reasonably likely to materially affect, the
registrant's internal control over financial
reporting.

The registrant's principal executive officer and principal financial
officer, however, voluntarily are reporting the following information:

In August of 2006 the registrant's investment adviser
enhanced its internal procedures for reporting performance
information required to be included in prospectuses.
Those enhancements involved additional internal controls
over the appropriateness of performance data
generated for this purpose.  Such enhancements were made
following an internal review which identified
prospectuses relating to certain classes of shares of
a limited number of registrants where, inadvertently,
performance information not reflecting the deduction of
applicable sales charges was included. Those prospectuses
were revised, and the revised prospectuses were distributed to
shareholders.


ITEM 12. EXHIBITS.

(a) File the exhibits listed below as part of this Form. Letter or number the
exhibits in the sequence indicated.

(1) Any code of ethics, or amendment thereto, that is the subject of the
disclosure required by Item 2, to the extent that the registrant intends to
satisfy the Item 2 requirements through filing of an exhibit.



(2) A separate certification for each principal executive officer and principal
financial officer of the registrant as required by Rule 30a-2(a) under the Act
(17 CFR 270.30a-2(a)) , exactly as set forth below:

Filed herewith.





                                   SIGNATURES

                          [See General Instruction F]


Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, the registrant has duly caused this report to be
signed on its behalf by the undersigned, thereunto duly authorized.


(Registrant) Pioneer Money Market Trust


By (Signature and Title)* /s/ Lisa M. Jones
Lisa M. Jones, President & Chief Executive Officer

Date August 29, 2017


Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, this report has been signed below by the
following persons on behalf of the registrant and in the capacities and on the
dates indicated.


By (Signature and Title)* /s/ Lisa M. Jones
Lisa M. Jones, President & Chief Executive Officer

Date August 29, 2017



By (Signature and Title)* /s/ Mark E. Bradley
Mark E. Bradley, Treasurer & Chief Accounting & Financial Officer

Date August 29, 2017


* Print the name and title of each signing officer under his or her signature.