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, Amundi Pioneer Asset 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, 2019 through June 30, 2019


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, 2019
--------------------------------------------------------------------------------

                            Ticker Symbols:

                            Class A   PMTXX
                            Class R   PRXXX
                            Class Y   PRYXX

Beginning in February 2021, as permitted by regulations adopted by the
Securities and Exchange Commission, paper copies of the Fund's shareholder
reports like this one will no longer be sent by mail, unless you specifically
request paper copies of the reports from the Fund or from your financial
intermediary, such as a broker-dealer, bank or insurance company. Instead, the
reports will be made available on the Fund's website, and you will be notified
by mail each time a report is posted and provided with a website link to access
the report.

If you already elected to receive shareholder reports electronically, you will
not be affected by this change and you need not take any action. You may elect
to receive shareholder reports and other communications electronically by
contacting your financial intermediary or, if you invest directly with the
Fund, by calling 1-800-225-6292.

You may elect to receive all future reports in paper free of charge. If you
invest directly with the Fund, you can inform the Fund that you wish to
continue receiving paper copies of your shareholder reports by calling
1-800-225-6292. If you invest through a financial intermediary, you can contact
your financial intermediary to request that you continue to receive paper
copies of your shareholder reports. Your election to receive reports in paper
will apply to all funds held in your account if you invest through your
financial intermediary or all funds held within the Pioneer Fund complex if you
invest directly.

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



                       visit us: www.amundipioneer.com/us



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                                                23

Trustees, Officers and Service Providers                                     30


       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 1



President's Letter

Since 1928, active portfolio management based on in-depth, fundamental
research, has been the foundation of Amundi Pioneer's investment approach. We
believe an active management investment strategy is a prudent approach to
investing, especially during periods of market volatility, which can result
from any number of risk factors, including slow U.S. economic growth, rising
interest rates, and geopolitical factors. Of course, in today's global economy,
risk factors extend well beyond U.S. borders. In fact, it's not unusual for
political and economic issues on the international front to cause or contribute
to volatility in U.S. markets.

At Amundi Pioneer, each security under consideration is researched by our team
of experienced investment professionals, who communicate directly with the
management teams of those companies. At the end of this research process, if we
have conviction in a company's business model and management team, and regard
the security as a potentially solid investment opportunity, an Amundi Pioneer
portfolio manager makes an active decision to invest in that security. The
portfolio resulting from these decisions represents an expression of his or her
convictions, and strives to balance overall risk and return opportunity.

As an example, the Standard & Poor's 500 Index -- the predominant benchmark for
many U.S. Large-Cap Core Equity funds -- has 500 stocks. An Amundi Pioneer
portfolio manager chooses to invest in only those companies that he or she
believes can offer the most attractive opportunities to pursue the fund's
investment objective, thus potentially benefiting the fund's shareowners. This
process results in a portfolio that does not own all 500 stocks, but a much
narrower universe.

The same active decision to invest in a company is also applied when we decide
to sell a security, either due to changing fundamentals, valuation concerns, or
market risks. We apply this active decision-making across all of our equity,
fixed-income, and global portfolios.

Today, as investors, we have many options. It is our view that active
management can serve shareholders well not only when markets are thriving, but
also during periods of market volatility and uncertainty, thus making it a
compelling investment choice. As you consider the many choices today, 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.

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



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 U.S.
Amundi Pioneer Asset Management USA, Inc.
June 30, 2019

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 | 6/30/19 3



Portfolio Management Discussion | 6/30/19

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 ended June 30, 2019. 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 first six-month period ended June 30,
      2019?

A     Pioneer U.S Government Money Market Fund's Class A shares returned 0.87%
      at net asset value during the six-month period ended June 30, 2019.

Q     How would you describe the environment for money market investing during
      the six-month period ended June 30, 2019?

A     The period began in the wake of four increases in the federal funds rate
      by the U.S. Federal Reserve (the Fed) during the 2018 calendar year, and
      speculation that more rate increases were to follow in 2019, as part of
      the Fed's policy to tighten money supply and constrain inflation. For the
      most part, the Fed had already met those goals, with the exception of
      achieving a target inflation rate of 2%. Over the six-month period, the
      Fed generally resisted calls for cuts in the federal funds rate, which
      normally has a strong influence over short-term interest rates.

      During the period, the yield on the one-year U.S. Treasury bill fell from
      2.60% to 1.93%, while the yields on the 3-month and 1-month Treasuries
      declined by less. The decline in yields was inconsistent with longer-term
      trends, as interest rates have typically increased in a good economy,
      especially when stock prices hit record highs. The pattern of declining
      market rates reflected the possibility of higher tariffs sparking the
      onset of a full-blown trade war among nations, particularly the U.S. and
      China, which could weaken the global economy.

Q     How did you manage the Fund's portfolio during the six-month period ended
      June 30, 2019?

A     Over the six-month period, we continually assessed relative values in the
      market, investing the Fund in securities that are in line with our
      investment philosophy. We maintained a conservative approach in managing
      the

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



      portfolio, consistent with the Fund's principal objectives, the primary
      one being to protect investors' capital by seeking to maintain a $1 net
      asset value for the Fund's shares. Our secondary goal is to maintain high
      liquidity in the portfolio by seeking to ensure that we can quickly sell
      any of the Fund's investments when necessary. Our third goal is to seek
      securities with attractive yields, which matches up with the first two
      goals of protecting shareholders' capital and maintaining liquidity.

      The majority of the Fund's holdings during the period were repurchase
      agreements collateralized by Treasury securities or government mortgages,
      the latter of which have the potential to earn greater yields than
      Treasuries. Most of the Fund's exposures were concentrated in securities
      with very short maturities, which therefore offered stronger price
      protection than debt instruments with longer maturities. In addition to
      repurchase agreements, we maintained portfolio holdings in straight U.S
      government securities, mostly at the short-end of the yield curve. (The
      yield curve is a line that plots the interest rates, at a set point in
      time, of bonds having equal credit quality, but differing maturity dates.)
      We also invested in government-agency securities, which generally offer
      higher yields than Treasuries.

      At period-end, the average maturity of the Fund's holdings was about 20
      days.

Q     What is your investment outlook?

A     We anticipate that the Fed will act to lower interest rates -- perhaps
      twice in the second half of 2019 -- in an effort to lengthen the economic
      cycle. If the Fed does ease monetary policy, that could allow for further
      gains in stock and bond prices.

      In managing the Fund, we intend to continue our focus on our main goals of
      price stability and the protection of shareholders' capital, while
      striving to provide a competitive yield.

       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 5



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. 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. 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.

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 | 6/30/19



Portfolio Summary | 6/30/19

Portfolio Diversification
--------------------------------------------------------------------------------
(As a percentage of total investments)*

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



                                                                        
U.S. Government Securities and Agency Obligations                          80.9%
Repurchase Agreements (Collateralized by U.S. Government Securities)       19.1%


10 Largest U.S. Government and Agency Obligations
--------------------------------------------------------------------------------
(As a percentage of total investments)*



                                                                                      
 1. U.S. Treasury Notes, 2.144% (3 Month U.S. Treasury Bill Money Market Yield +
    5 bps), 10/31/19                                                                     10.28%
-----------------------------------------------------------------------------------------------
 2. U.S. Treasury Notes, 2.156% (3 Month U.S. Treasury Bill Money Market Yield +
    6 bps), 7/31/19                                                                      10.28
-----------------------------------------------------------------------------------------------
 3. U.S. Treasury Bills, 8/1/19                                                          10.00
-----------------------------------------------------------------------------------------------
 4. U.S. Treasury Bills, 7/16/19                                                          9.78
-----------------------------------------------------------------------------------------------
 5. U.S. Treasury Bills, 7/2/19                                                           4.46
-----------------------------------------------------------------------------------------------
 6. U.S. Treasury Notes, 2.25%, 2/29/20                                                   3.49
-----------------------------------------------------------------------------------------------
 7. U.S. Treasury Notes, 2.139% (3 Month U.S. Treasury Bill Money Market Yield +
    4 bps), 7/31/20                                                                       3.05
-----------------------------------------------------------------------------------------------
 8. U.S. Treasury Notes, 2.141% (3 Month U.S. Treasury Bill Money Market Yield +
    5 bps), 10/31/20                                                                      3.05
-----------------------------------------------------------------------------------------------
 9. U.S. Treasury Notes, 2.211% (3 Month U.S. Treasury Bill Money Market Yield +
    12 bps), 1/31/21                                                                      2.57
-----------------------------------------------------------------------------------------------
10. U.S. Treasury Notes, 2.129% (3 Month U.S. Treasury Bill Money Market Yield +
    3 bps), 4/30/20                                                                       2.57
-----------------------------------------------------------------------------------------------


*     Excludes derivative contracts except for options purchased. The Fund is
      actively managed, and current holdings may be different. The holdings
      listed should not be considered recommendations to buy or sell any
      securities.

       Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 7



Prices and Distributions | 6/30/19

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



--------------------------------------------------------------------------------
     Class                  6/30/19                     12/31/18
--------------------------------------------------------------------------------
                                                    
      A                      $1.00                        $1.00
--------------------------------------------------------------------------------
      R                      $1.00                        $1.00
--------------------------------------------------------------------------------
      Y                      $1.00                        $1.00
--------------------------------------------------------------------------------


Distributions per Share: 1/1/19 - 6/30/19
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
                                       Short-Term            Long-Term
     Class          Dividends         Capital Gains         Capital Gains
--------------------------------------------------------------------------------
                                                     
      A             $0.0088             $ --                  $ --
--------------------------------------------------------------------------------
      R             $0.0069             $ --                  $ --
--------------------------------------------------------------------------------
      Y             $0.0097             $ --                  $ --
--------------------------------------------------------------------------------


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



--------------------------------------------------------------------------------
     Class               7-Day Annualized*             7-Day Effective**
--------------------------------------------------------------------------------
                                                     
      A                       1.55%                        1.56%
--------------------------------------------------------------------------------
      R                       1.15%                        1.15%
--------------------------------------------------------------------------------
      Y                       1.74%                        1.75%
--------------------------------------------------------------------------------


*     The 7-day annualized net yield describes the annualized income earned over
      a 7-day period.

**    The 7-day effective yield describes the amount one is expected to earn
      over a 1-year period assuming that dividends are reinvested at the average
      rate of the last 7-days.

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



Expense Ratio (Per prospectus dated May 1, 2019)
--------------------------------------------------------------------------------



--------------------------------------------------------------------------------
     Class                                Gross
--------------------------------------------------------------------------------
                                       
      A                                   0.81%
--------------------------------------------------------------------------------
      R                                   1.08%
--------------------------------------------------------------------------------
      Y                                   0.54%
--------------------------------------------------------------------------------


Call 1-800-225-6292 or visit www.amundipioneer.com/us 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.

Please refer to the financial highlights for a more current expense ratio.

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 | 6/30/19 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, 2019, through June 30, 2019.



--------------------------------------------------------------------------------
Share Class                             A               R               Y
--------------------------------------------------------------------------------
                                                           
Beginning Account                   $1,000.00       $1,000.00       $1,000.00
Value on 1/1/19
--------------------------------------------------------------------------------
Ending Account                      $1,008.70       $1,006.80       $1,009.60
Value on 6/30/19
--------------------------------------------------------------------------------
Expenses Paid                           $3.29           $5.47           $2.39
During Period*
--------------------------------------------------------------------------------


*     Expenses are equal to the Fund's annualized net expense ratio of 0.66%,
      1.10% and 0.48% for Class A, Class R 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 | 6/30/19



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, 2019, through June 30, 2019.



--------------------------------------------------------------------------------
Share Class                             A               R               Y
--------------------------------------------------------------------------------
                                                           
Beginning Account                   $1,000.00       $1,000.00       $1,000.00
Value on 1/1/19
--------------------------------------------------------------------------------
Ending Account                      $1,021.52       $1,019.34       $1,022.41
Value on 6/30/19
--------------------------------------------------------------------------------
Expenses Paid                           $3.31           $5.51           $2.41
During Period*
--------------------------------------------------------------------------------


*     Expenses are equal to the Fund's annualized net expense ratio of 0.66%,
      1.10% and 0.48% for Class A, Class R 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 | 6/30/19 11



Schedule of Investments | 6/30/19 (unaudited)



--------------------------------------------------------------------------------------------------
Principal
Amount ($)                                                                            Value
--------------------------------------------------------------------------------------------------
                                                                                
                      UNAFFILIATED ISSUERS -- 80.7%
                      U.S. GOVERNMENT AND AGENCY
                      OBLIGATIONS -- 80.7% of Net Assets
    4,029,000(a)      Fannie Mae Discount Notes, 7/24/19                              $  4,023,311
      520,000(b)      Federal Farm Credit Banks, 2.331% (1 Month USD LIBOR -
                      8 bps), 11/13/19                                                     519,933
      500,000(b)      Federal Farm Credit Banks, 2.39% (1 Month USD LIBOR +
                      0 bps), 6/19/20                                                      500,032
    1,310,000(b)      Federal Farm Credit Banks, 2.402% (1 Month USD LIBOR +
                      0 bps), 5/26/20                                                    1,309,900
    1,305,000(b)      Federal Farm Credit Banks, 2.404% (1 Month USD LIBOR +
                      0 bps), 9/25/20                                                    1,304,779
    1,550,000(b)      Federal Farm Credit Banks, 2.433% (1 Month USD LIBOR +
                      5 bps), 2/21/20                                                    1,550,681
    3,725,000(b)      Federal Farm Credit Banks, 2.462% (1 Month USD LIBOR +
                      5 bps), 2/10/20                                                    3,727,355
      360,000(b)      Federal Farm Credit Banks, 2.584% (1 Month USD LIBOR +
                      19 bps), 7/15/19                                                     360,040
    1,400,000(a)      Federal Home Loan Bank Discount Notes, 7/3/19                      1,399,827
    2,200,000(a)      Federal Home Loan Bank Discount Notes, 7/5/19                      2,199,457
    3,100,000(a)      Federal Home Loan Bank Discount Notes, 7/9/19                      3,098,471
    1,500,000(a)      Federal Home Loan Bank Discount Notes, 7/10/19                     1,499,164
    2,300,000(a)      Federal Home Loan Bank Discount Notes, 7/12/19                     2,298,440
    2,000,000(a)      Federal Home Loan Bank Discount Notes, 7/17/19                     1,998,027
    3,740,000(a)      Federal Home Loan Bank Discount Notes, 7/19/19                     3,735,792
      400,000(a)      Federal Home Loan Bank Discount Notes, 8/2/19                        399,211
    4,500,000(a)      Federal Home Loan Bank Discount Notes, 8/20/19                     4,486,219
      700,000(a)      Federal Home Loan Bank Discount Notes, 9/4/19                        697,194
      730,000         Federal Home Loan Banks, 2.0%, 9/13/19                               729,446
      300,000(b)      Federal Home Loan Banks, 2.32% (1 Month USD LIBOR -
                      7 bps), 7/19/19                                                      299,995
    1,000,000(b)      Federal Home Loan Banks, 2.322% (1 Month USD LIBOR -
                      8 bps), 9/26/19                                                      999,965
    1,000,000(b)      Federal Home Loan Banks, 2.323% (1 Month USD LIBOR -
                      6 bps), 2/20/20                                                      999,982
      600,000(b)      Federal Home Loan Banks, 2.339% (1 Month USD LIBOR -
                      6 bps), 12/16/19                                                     599,999
      400,000(b)      Federal Home Loan Banks, 2.339% (1 Month USD LIBOR -
                      7 bps), 1/23/20                                                      399,975
    1,500,000(b)      Federal Home Loan Banks, 2.359% (1 Month USD LIBOR -
                      6 bps), 8/7/19                                                     1,500,064
      730,000(b)      Federal Home Loan Banks, 2.435% (3 Month USD LIBOR -
                      16 bps), 7/5/19                                                      729,999
    1,255,000(b)      Federal Home Loan Banks, 2.445% (SOFRRATE +
                      3 bps), 9/20/19                                                    1,255,014


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

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





--------------------------------------------------------------------------------------------------
Principal
Amount ($)                                                                            Value
--------------------------------------------------------------------------------------------------
                                                                                
                      U.S. GOVERNMENT AND AGENCY
                      OBLIGATIONS -- (continued)
    3,290,000(b)      Federal Home Loan Mortgage Corp., 2.433% (3 Month
                      USD LIBOR - 17 bps), 7/5/19                                     $  3,290,000
    1,000,000(b)      Federal National Mortgage Association, 2.52%
                      (SOFRRATE + 10 bps), 4/30/20                                       1,000,559
    4,030,000(b)      Federal National Mortgage Association, 2.58%
                      (SOFRRATE + 16 bps), 1/30/20                                       4,033,286
   10,700,000(a)      U.S. Treasury Bills, 7/2/19                                       10,699,315
   23,500,000(a)      U.S. Treasury Bills, 7/16/19                                      23,478,692
   24,040,000(a)      U.S. Treasury Bills, 8/1/19                                       23,996,784
    6,170,000(b)      U.S. Treasury Notes, 2.129% (3 Month U.S. Treasury Bill
                      Money Market Yield + 3 bps), 4/30/20                               6,169,212
    7,325,000(b)      U.S. Treasury Notes, 2.139% (3 Month U.S. Treasury Bill
                      Money Market Yield + 4 bps), 7/31/20                               7,323,099
    7,325,000(b)      U.S. Treasury Notes, 2.141% (3 Month U.S. Treasury Bill
                      Money Market Yield + 5 bps), 10/31/20                              7,320,848
   24,685,000(b)      U.S. Treasury Notes, 2.144% (3 Month U.S. Treasury Bill
                      Money Market Yield + 5 bps), 10/31/19                             24,688,916
   24,685,000(b)      U.S. Treasury Notes, 2.156% (3 Month U.S. Treasury Bill
                      Money Market Yield + 6 bps), 7/31/19                              24,687,065
    6,180,000(b)      U.S. Treasury Notes, 2.211% (3 Month U.S. Treasury Bill
                      Money Market Yield + 12 bps), 1/31/21                              6,179,522
    8,390,000         U.S. Treasury Notes, 2.25%, 2/29/20                                8,374,163
      370,000         U.S. Treasury Notes, 3.375%, 11/15/19                                370,982
--------------------------------------------------------------------------------------------------
                      TOTAL U.S. GOVERNMENT AND AGENCY OBLIGATIONS
                      (Cost $194,234,715)                                             $194,234,715
--------------------------------------------------------------------------------------------------
                      TEMPORARY CASH INVESTMENTS -- 19.1%
                      of Net Assets
                      REPURCHASE AGREEMENTS -- 19.1%
    3,850,000         $3,850,000 TD Securities USA LLC, 2.49%,
                      dated 6/30/19 plus accrued interest on 7/1/19,
                      collateralized by $3,927,090 U.S. Treasury Notes,
                      2.63%, 6/15/21.                                                 $  3,850,000
    6,000,000         $6,000,000 TD Securities USA LLC, 2.51%,
                      dated 6/30/19 plus accrued interest on 7/1/19,
                      collateralized by $6,120,001 Freddie Mac Giant,
                      4%, 10/1/48.                                                       6,000,000
   12,000,000         $12,000,000 RBC Capital Markets LLC, 2.48%,
                      dated 6/30/19 plus accrued interest on 7/1/19
                      collateralized by the following:
                      $3,456,681 Freddie Mac Giant,
                      3.5 -- 4.5%, 9/1/42 -- 4/1/49
                      $8,521,144 Federal National Mortgage Association,
                      3.5% -- 4%, 3/1/41 -- 4/1/49
                      $264,705 Government National Mortgage Association,
                      4.5%, 4/20/49.                                                    12,000,000


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

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 13



Schedule of Investments | 6/30/19 (unaudited) (continued)



--------------------------------------------------------------------------------------------------
Principal
Amount ($)                                                                            Value
--------------------------------------------------------------------------------------------------
                                                                                
                      REPURCHASE AGREEMENTS -- (continued)
   12,000,000         $12,000,000 ScotiaBank, 2.45%, dated 6/30/19
                      plus accrued interest on 7/1/19, collateralized
                      by the following:
                      $28 Federal National Mortgage Association, 6.5%, 7/1/36
                      $3,995,107 Freddie Mac Giant, 4.5% -- 4.6%,
                      10/1/40 -- 11/1/48
                      $8,247,421 U.S. Treasury Notes, 2%, 5/31/2024.                  $ 12,000,000
   12,000,000         $12,000,000 Merril Lynch, Pierce, Fenner & Smith Inc.,
                      2.49%, dated 6/30/19 plus accrued interest on
                      7/1/19, collateralized by
                      $12,240,000 Government National Mortgage
                      Association, 4%, 2/20/49.                                         12,000,000
                                                                                      ------------
                                                                                      $ 45,850,000
--------------------------------------------------------------------------------------------------
                      TOTAL TEMPORARY CASH INVESTMENTS
                      (Cost $45,850,000)                                              $ 45,850,000
--------------------------------------------------------------------------------------------------
                      TOTAL INVESTMENT IN SECURITIES OF
                      UNAFFILIATED ISSUERS -- 99.8%
                      (Cost $240,084,715)                                             $240,084,715
--------------------------------------------------------------------------------------------------
                      OTHER ASSETS & LIABILITIES -- 0.2%                              $    576,761
--------------------------------------------------------------------------------------------------
                      NET ASSETS -- 100.0%                                            $240,661,476
==================================================================================================


bps        Basis Points.

LIBOR      London Interbank Offered Rate.

SOFRRATE   Secured Overnight Financing Rate.

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

(b)        Floating rate note. Coupon rate, reference index and spread shown at
           June 30, 2019.

At June 30, 2019, the net unrealized depreciation on investments based on cost
for federal tax purposes of $240,084,907 was as follows:



                                                                                
        Aggregate gross unrealized appreciation for all investments in which
         there is an excess of value over tax cost                                 $  --
        Aggregate gross unrealized depreciation for all investments in which
         there is an excess of tax cost over value                                  (192)
                                                                                   -----
        Net unrealized depreciation                                                $(192)
                                                                                   =====


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

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



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, 2019, in valuing
the Fund's investments.



------------------------------------------------------------------------------------
                              Level 1     Level 2          Level 3     Total
------------------------------------------------------------------------------------
                                                           
U.S. Government and
  Agency Obligations          $ --        $194,234,715     $ --        $194,234,715
Repurchase Agreements           --          45,850,000       --          45,850,000
------------------------------------------------------------------------------------
Total                         $ --        $240,084,715     $ --        $240,084,715
====================================================================================


During the six months ended June 30, 2019, 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 | 6/30/19 15



Statement of Assets and Liabilities | 6/30/19 (unaudited)



                                                                             
ASSETS:
  Investments in unaffiliated issuers, at value (cost $240,084,715)             $240,084,715
  Cash                                                                               539,964
  Receivables --
     Fund shares sold                                                                337,643
     Interest                                                                        453,772
  Other assets                                                                        33,390
--------------------------------------------------------------------------------------------
       Total assets                                                             $241,449,484
============================================================================================
LIABILITIES:
  Payables --
     Fund shares repurchased                                                    $    520,403
     Distributions                                                                    99,524
     Trustees' fees                                                                      734
     Administrative fees                                                              34,048
     Professional fees                                                                22,186
     Transfer agent fees                                                              27,806
     Shareowner communications expense                                                43,807
  Due to affiliates                                                                   13,114
  Accrued expenses                                                                    26,386
--------------------------------------------------------------------------------------------
       Total liabilities                                                        $    788,008
============================================================================================
NET ASSETS:
  Paid-in capital                                                               $240,658,003
  Distributable earnings                                                               3,473
--------------------------------------------------------------------------------------------
       Net assets                                                               $240,661,476
============================================================================================
NET ASSET VALUE PER SHARE:
No par value (unlimited number of shares authorized)
  Class A (based on $195,727,183/195,878,620 shares)                            $       1.00
  Class R (based on $656,674/656,973 shares)                                    $       1.00
  Class Y (based on $44,277,619/44,290,544 shares)                              $       1.00
============================================================================================


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

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



Statement of Operations (unaudited)

For the Six Months Ended 6/30/19



                                                                         
INVESTMENT INCOME:
  Interest from unaffiliated issuers                           $2,923,888
------------------------------------------------------------------------------------------
        Total investment income                                                $2,923,888
------------------------------------------------------------------------------------------
EXPENSES:
  Management fees                                              $  423,453
  Administrative expense                                           88,286
  Transfer agent fees
     Class A                                                      101,446
     Class R                                                          287
     Class Y                                                           23
  Distribution fees
     Class A                                                      149,804
     Class R                                                        1,543
  Shareowner communications expense                                69,064
  Custodian fees                                                   12,401
  Registration fees                                                29,139
  Professional fees                                                30,715
  Printing expense                                                  5,000
  Trustees' fees                                                    2,856
  Insurance expense                                                    92
  Miscellaneous                                                     3,253
------------------------------------------------------------------------------------------
     Total expenses                                                            $  917,362
     Less waiver of Class A distribution fees                                    (149,804)
------------------------------------------------------------------------------------------
     Net expenses                                                              $  767,558
------------------------------------------------------------------------------------------
        Net investment income                                                  $2,156,330
------------------------------------------------------------------------------------------
REALIZED GAIN (LOSS) ON INVESTMENTS:
  Net realized gain (loss) on investments                                      $    8,690
------------------------------------------------------------------------------------------
  Net increase in net assets resulting from operations                         $2,165,020
==========================================================================================


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

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



Statements of Changes in Net Assets



----------------------------------------------------------------------------------------------------------
                                                                  Six Months
                                                                  Ended
                                                                  6/30/19                   Year Ended
                                                                  (unaudited)               12/31/18
----------------------------------------------------------------------------------------------------------
                                                                                      
FROM OPERATIONS:
Net investment income (loss)                                      $  2,156,330              $   3,123,719
Net realized gain (loss) on investments                                  8,690                      1,783
----------------------------------------------------------------------------------------------------------
     Net increase in net assets resulting
        from operations                                           $  2,165,020              $   3,125,502
----------------------------------------------------------------------------------------------------------
DISTRIBUTIONS TO SHAREOWNERS:
Class A ($0.0088 and $0.0122 per share, respectively)             $ (1,751,218)             $  (2,477,955)
Class R ($0.0069 and $0.0079 per share, respectively)                   (4,256)                    (3,611)
Class Y ($0.0097 and $0.0136 per share, respectively)                 (402,059)                  (644,614)
----------------------------------------------------------------------------------------------------------
        Total distributions to shareowners                        $ (2,157,533)             $  (3,126,180)
----------------------------------------------------------------------------------------------------------
FROM FUND SHARE TRANSACTIONS:
Net proceeds from sales of shares                                 $ 56,572,140              $ 133,461,302
Reinvestment of distributions                                        1,715,799                  2,437,120
Cost of shares repurchased                                         (65,832,464)              (154,283,380)
----------------------------------------------------------------------------------------------------------
     Net decrease in net assets resulting from Fund
        share transactions                                        $ (7,544,525)             $ (18,384,958)
----------------------------------------------------------------------------------------------------------
     Net decrease in net assets                                   $ (7,537,038)             $ (18,385,636)
NET ASSETS:
Beginning of period                                               $248,198,514              $ 266,584,150
----------------------------------------------------------------------------------------------------------
End of period                                                     $240,661,476              $ 248,198,514
==========================================================================================================


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

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





-------------------------------------------------------------------------------------------------------
                                     Six Months      Six Months
                                     Ended           Ended
                                     6/30/19         6/30/19           Year Ended        Year Ended
                                     Shares          Amount            12/31/18          12/31/18
                                     (unaudited)     (unaudited)       Shares            Amount
-------------------------------------------------------------------------------------------------------
                                                                             
Class A
Shares sold                          40,884,762      $ 40,884,762       116,205,585      $ 116,205,585
Reinvestment of distributions         1,709,551         1,709,551         2,429,530          2,429,530
Less shares repurchased             (57,163,329)      (57,163,330)     (125,600,716)      (125,600,716)
-------------------------------------------------------------------------------------------------------
     Net decrease                   (14,569,016)     $(14,569,017)       (6,965,601)     $  (6,965,601)
=======================================================================================================
Class R
Shares sold                             476,909      $    476,909           783,652      $     783,652
Reinvestment of distributions             3,875             3,875             3,196              3,049
Less shares repurchased                (377,175)         (377,175)         (384,029)          (384,029)
-------------------------------------------------------------------------------------------------------
     Net increase                       103,609      $    103,609           402,819      $     402,672
=======================================================================================================
Class Y
Shares sold                          15,210,469      $ 15,210,469        16,472,065      $  16,472,065
Reinvestment of distributions             2,373             2,373             4,541              4,541
Less shares repurchased              (8,291,959)       (8,291,959)      (28,298,635)       (28,298,635)
-------------------------------------------------------------------------------------------------------
     Net increase (decrease)          6,920,883      $  6,920,883       (11,822,029)     $ (11,822,029)
=======================================================================================================


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

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



Financial Highlights



------------------------------------------------------------------------------------------------------------------------------------
                                                   Six Months
                                                   Ended         Year        Year        Year            Year           Year
                                                   6/30/19       Ended       Ended       Ended           Ended          Ended
                                                   (unaudited)   12/31/18    12/31/17    12/31/16*       12/31/15*      12/31/14*
------------------------------------------------------------------------------------------------------------------------------------
                                                                                                      
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)                     $  0.009(a)  $  0.012(a)  $  0.003(a) $  0.000(a)(b)  $  0.000(a)(b) $  0.000(b)
------------------------------------------------------------------------------------------------------------------------------------
Distributions to shareowners:
  Net investment income                            $ (0.009)    $ (0.012)(c) $ (0.003)   $ (0.000)(b)(c) $ (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 (d)                                       0.87%(e)     1.21%        0.27%       0.01%           0.01%          0.01%
Ratio of net expenses to average net assets (f)        0.66%(g)     0.66%        0.62%       0.34%           0.10%          0.05%
Ratio of net investment income (loss) to average
  net assets                                           1.74%(g)     1.20%        0.26%       0.01%           0.01%          0.01%
Net assets, end of period (in thousands)           $195,727     $210,290     $217,256    $251,143        $261,928       $273,746
Ratios with no waiver of fees and assumption of
  expenses by the Adviser and no reduction for
  fees paid indirectly:
  Total expenses to average net assets (f)             0.81%(g)     0.81%        0.80%       0.82%           0.71%          0.75%
  Net investment income (loss) to average net
  assets                                               1.59%(g)     1.05%        0.08%      (0.46)%         (0.60)%        (0.69)%
====================================================================================================================================


*     The Fund was audited by an independent registered public accounting firm
      other than Ernst & Young LLP.

(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)   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.

(d)   Assumes initial investment at net asset value at the beginning of each
      period, reinvestment of all distributions and 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.

(e)   Not annualized.

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

(g)   Annualized.

+     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 | 6/30/19





----------------------------------------------------------------------------------------------------------------------
                                                                           Six Months
                                                                           Ended           Year
                                                                           6/30/19         Ended           8/1/17* to
                                                                           (unaudited)     12/31/18        12/31/17
----------------------------------------------------------------------------------------------------------------------
                                                                                                  
Class R
Net asset value, beginning of period                                       $  1.00         $   1.00        $  1.00
----------------------------------------------------------------------------------------------------------------------
Increase (decrease) from investment operations:
  Net investment income (loss) (a)                                         $ 0.007         $ 0.009         $ 0.000(b)
  Net realized and unrealized gain (loss) on investments                     0.000           (0.001)         0.000
----------------------------------------------------------------------------------------------------------------------
Net increase (decrease) from investment operations                         $ 0.007         $ 0.008         $ 0.000
----------------------------------------------------------------------------------------------------------------------
Distributions to shareowners:
  Net investment income                                                    $(0.007)        $(0.008)(c)     $(0.000)(b)
----------------------------------------------------------------------------------------------------------------------
Net asset value, end of period                                             $  1.00         $   1.00        $  1.00
======================================================================================================================
Total return (d)                                                              0.68%(e)        0.78%           0.03%(e)
Ratio of net expenses to average net assets                                   1.10%(f)        1.08%           1.02%(f)
Ratio of net investment income (loss) to average net assets                   1.31%(f)        0.85%           0.10%(f)
Net assets, end of period (in thousands)                                   $   657         $    553        $   151
Ratios with no waiver of fees and assumption of expenses
  by the Adviser and no reduction for fees paid indirectly:
  Total expenses to average net assets                                        1.10%(f)        1.08%           1.03%(f)
  Net investment income (loss) to average net assets                          1.31%(f)        0.85%           0.09%(f)
======================================================================================================================


*     Class R shares commenced operations on August 1, 2017.

(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)   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.

(d)   Assumes initial investment at net asset value at the beginning of each
      period, reinvestment of all distributions and the complete redemption of
      the investment at net asset value at the end of each period.

(e)   Not annualized.

(f)   Annualized.

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

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 21



Financial Highlights (continued)



------------------------------------------------------------------------------------------------------------------------------------
                                                       Six Months
                                                       Ended       Year        Year       Year           Year          Year
                                                       6/30/19     Ended       Ended      Ended          Ended         Ended
                                                       (unaudited) 12/31/18    12/31/17   12/31/16*      12/31/15*     12/31/14*
------------------------------------------------------------------------------------------------------------------------------------
                                                                                                     
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)                         $ 0.010(a)  $ 0.013(a)  $ 0.004(a) $ 0.000(a)(b)  $ 0.000(a)(b) $ 0.000(b)
  Net realized and unrealized gain (loss) on
  investments                                            0.000       0.001       0.000      0.000          0.000         0.000
------------------------------------------------------------------------------------------------------------------------------------
Net increase (decrease) from investment operations     $ 0.010     $ 0.014     $ 0.004    $ 0.000        $ 0.000       $ 0.000
------------------------------------------------------------------------------------------------------------------------------------
Distributions to shareowners:
  Net investment income                                $(0.010)    $(0.014)(c) $(0.004)   $(0.000)(b)(c) $(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 (d)                                          0.96%(e)    1.34%       0.37%      0.01%          0.01%         0.01%
Ratio of net expenses to average net assets (f)           0.48%(g)    0.54%       0.51%      0.34%          0.10%         0.05%
Ratio of net investment income (loss) to average
  net assets                                              1.92%(g)    1.30%       0.36%      0.01%          0.01%         0.01%
Net assets, end of period (in thousands)               $44,278     $37,356     $49,178    $63,703        $63,553       $58,851
Ratios with no waiver of fees and assumption of
  expenses by the Adviser and no reduction for fees
  paid indirectly:
  Total expenses to average net assets (f)                0.48%(g)    0.54%       0.51%      0.50%          0.46%         0.46%
  Net investment income (loss) to average net assets      1.92%(g)    1.30%       0.36%     (0.15)%        (0.35)%       (0.40)%
====================================================================================================================================


*     The Fund was audited by an independent registered public accounting firm
      other than Ernst & Young LLP.

(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)   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.

(d)   Assumes initial investment at net asset value at the beginning of each
      period, reinvestment of all distributions and the complete redemption of
      the investment at net asset value at the end of each period.

(e)   Not annualized.

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

(g)   Annualized.

+     Amount rounds to less than 0.01%.

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

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



Notes to Financial Statements | 6/30/19 (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 offers three classes of shares designated as Class A, Class R and
Class Y shares. Class R shares commenced operations on August 1, 2017. 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.

Amundi Pioneer Asset Management, Inc., an indirect, wholly owned subsidiary of
Amundi and Amundi's wholly owned subsidiary, Amundi USA, Inc., serves as the
Fund's investment adviser (the "Adviser"). Amundi Pioneer Distributor, Inc., an
affiliate of Amundi Pioneer Asset Management, Inc., serves as the Fund's
distributor (the "Distributor").

In August 2018, the Securities and Exchange Commission ("SEC") released a
Disclosure Update and Simplification Final Rule. The Final Rule amends
Regulation S-X disclosures requirements to conform them to U.S. Generally
Accepted Accounting Principles ("U.S. GAAP") for investment companies. The
Fund's financial statements were prepared in compliance with the new amendments
to Regulation S-X.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 23



The Fund is an investment company and follows investment company accounting and
reporting guidance under U.S. GAAP. U.S. GAAP requires 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 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 twice daily, on each day the
      New York Stock Exchange ("NYSE") is open, at 1:00 p.m. Eastern time and as
      of the close of regular trading on the NYSE (normally 4:00 p.m. Eastern
      time).

      The Fund generally values its securities using the amortized cost method,
      which approximates fair market value, in accordance with Rule 2a-7 under
      the 1940 Act. This valuation method assumes a steady rate of amortization
      of any premium or discount from the date of purchase until the maturity of
      each security. This valuation method is designed to permit a money market
      fund to maintain a constant net asset value of $1.00 per share, but there
      is no guarantee that it will do so.

      Repurchase agreements are valued at par. Cash may included overnight time
      deposits at approved financial institutions.

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

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



      its shareowners. Therefore, no provision for federal income taxes is
      required. As of December 31, 2018, 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 on 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 over distributions 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 will be determined
      at the end of the current taxable year. The tax character of distributions
      paid during the year ended December 31, 2018 was as follows:



      --------------------------------------------------------------------------
                                                                           2018
      --------------------------------------------------------------------------
                                                                  
      Distributions paid from:
      Ordinary income                                                $3,126,180
      --------------------------------------------------------------------------
          Total                                                      $3,126,180
      ==========================================================================


      The following shows the components of distributable earnings (loss) on a
      federal income tax basis at December 31, 2018:



      --------------------------------------------------------------------------
                                                                           2018
      --------------------------------------------------------------------------
                                                                     
      Distributable earnings (loss):
      Other book/tax temporary differences                              $(4,014)
      --------------------------------------------------------------------------
          Total                                                         $(4,014)
      ==========================================================================


      The difference between book-basis and tax-basis net unrealized
      appreciation/(depreciation) are attributable to the tax deferral of losses
      on wash sales.

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.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 25



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 and Class R shares of the Fund, respectively
      (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, Class R and Class Y shares can
      reflect different transfer agent and distribution expense rates.

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 sectors. The Fund's investments
      in foreign markets and countries with limited developing markets may
      subject the Fund to a greater degree of risk than investments in a
      developed market. These risks include disruptive political or economic
      conditions and the imposition of adverse governmental laws or currency
      exchange restrictions.

      With the increased use of technologies such as the Internet to conduct
      business, the Fund is susceptible to operational, information security and
      related risks. While the Fund's Adviser has established business
      continuity plans in the event of, and risk management systems to prevent,
      limit or mitigate, such cyber-attacks, there are inherent limitations in
      such plans and systems, including the possibility that certain risks have
      not been identified. Furthermore, the Fund cannot control the
      cybersecurity plans and systems put in place by service providers to the
      Fund such as Brown Brothers

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



      Harriman & Co., the Fund's custodian and accounting agent, and DST Asset
      Manager Solutions, Inc., the Fund's transfer agent. In addition, many
      beneficial owners of Fund shares hold them through accounts at
      broker-dealers, retirement platforms and other financial market
      participants over which neither the Fund nor Amundi Pioneer exercises
      control. Each of these may in turn rely on service providers to them,
      which are also subject to the risk of cyber-attacks. Cybersecurity
      failures or breaches at Amundi Pioneer or the Fund's service providers or
      intermediaries have the ability to cause disruptions and impact business
      operations, potentially resulting in financial losses, interference with
      the Fund's ability to calculate its net asset value, impediments to
      trading, the inability of Fund shareowners to effect share purchases,
      redemptions or exchanges or receive distributions, loss of or unauthorized
      access to private shareowner information and violations of applicable
      privacy and other laws, regulatory fines, penalties, reputational damage,
      or additional compliance costs. Such costs and losses may not be covered
      under any insurance. In addition, maintaining vigilance against
      cyber-attacks may involve substantial costs over time, and system
      enhancements may themselves be subject to cyber-attacks.

      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 sub-custodian of the
      Fund. The Adviser 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, 2019 are disclosed in the Fund's
      Schedule of Investments.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 27



2. Management Agreement

The Adviser 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 the Fund's average daily net assets over $1 billion. For
the six months ended June 30, 2019, the net management fee was equivalent to
0.35% (annualized) of the Fund's average daily net assets.

The Adviser 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, the Adviser 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.
Additionally, the Adviser has voluntarily agreed to waive distribution fees for
Class A shares. These expense limitation policies are voluntary and temporary
and may be revised or terminated by the Adviser, at any time without notice.
Fees waived and expenses reimbursed during the six months ended June 30, 2019
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
$13,069 in management fees, administrative costs and certain other
reimbursements payable to the Adviser at June 30, 2019.

3. Transfer Agent

DST Asset Manager Solutions, Inc. 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, 2019, such out-of-pocket expenses by class of shares were
as follows:



--------------------------------------------------------------------------------
Shareowner Communications:
--------------------------------------------------------------------------------
                                                                     
Class A                                                                 $69,011
Class R                                                                      53
--------------------------------------------------------------------------------
 Total                                                                  $69,064
================================================================================


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



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 and Class R
shares. Pursuant to the Plan, the Fund pays the Distributor 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 shares. Pursuant to the Plan, the Fund further pays the
Distributor 0.50% of the average daily net assets attributable to Class R
shares for distribution services. Included in "Due to affiliates" reflected on
the Statement of Assets and Liabilities is $45 in distribution fees payable to
the Distributor, at June 30, 2019.

The Fund also has adopted a separate service plan for Class R shares (the
"Service Plan"). The Service Plan authorizes the Fund to pay securities
dealers, plan administrators or other service organizations that agree to
provide certain services to retirement plans or plan participants holding
shares of the Fund a service fee of up to 0.25% of the Fund's average daily net
assets attributable to Class R shares held by such plans.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 29



Trustees, Officers and Service Providers

Trustees                          Officers
Thomas J. Perna, Chairman         Lisa M. Jones, President and
David R. Bock                       Chief Executive Officer
Diane Durnin                      Mark E. Bradley, Treasurer and
Benjamin M. Friedman                Chief Financial and
Margaret B.W. Graham                Accounting 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.

Custodian and Sub-Administrator
Brown Brothers Harriman & Co.

Principal Underwriter
Amundi Pioneer Distributor, Inc.

Legal Counsel
Morgan, Lewis & Bockius LLP

Transfer Agent
DST Asset Manager Solutions, 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/us. This information is also available on
the Securities and Exchange Commission's web site at www.sec.gov.

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



                          This page is for your notes.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 31



                          This page is for your notes.

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



                          This page is for your notes.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 33



                          This page is for your notes.

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



                          This page is for your notes.

      Pioneer U.S. Government Money Market Fund | Semiannual Report | 6/30/19 35



                          This page is for your notes.

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



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

FactFoneSM 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 219427
Kansas City, MO 64121-9427

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

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

Visit our web site: www.amundipioneer.com/us

This report must be preceded or accompanied by a prospectus.

The Fund files a complete schedule of portfolio holdings with the Securities
and Exchange Commission for the first and third quarters of each fiscal year as
an exhibit to its reports on Form N-PORT. Shareholders may view the filed Form
N-PORT by visiting the Commission's web site at https://www.sec.gov.



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

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

Securities offered through Amundi Pioneer Distributor, Inc.
60 State Street, Boston, MA 02109
Underwriter of Pioneer Mutual Funds, Member SIPC
[C] 2019 Amundi Pioneer Asset Management 19399-13-0819



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)).

Mr. David R. Bock, 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 Amudi Pioneer Asset Management, Inc, 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.

Non-Audit Services
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. Disclosure of Securities Lending Activities for Closed-End
Management Investment Companies.

(a) If the registrant is a closed-end management investment company,
provide the following dollar amounts of income and compensation related
to the securities lending activities of the registrant during its most
recent fiscal year:

N/A

(1) Gross income from securities lending activities;

N/A

(2) All fees and/or compensation for each of the following securities
lending activities and related services: any share of revenue generated
by the securities lending program paid to the securities lending agent(s)
(revenue split); fees paid for cash collateral management services
(including fees deducted from a pooled cash collateral reinvestment
vehicle) that are not included in the revenue split; administrative
fees that are not included in the revenue split; fees for
indemnification that are not included in the revenue split; rebates
paid to borrowers; and any other fees relating to the securities lending
program that are not included in the revenue split, including a description
of those other fees;

N/A

(3) The aggregate fees/compensation disclosed pursuant to paragraph (2); and

N/A

(4) Net income from securities lending activities (i.e., the dollar amount in
paragraph (1) minus the dollar amount in paragraph (3)).

If a fee for a service is included in the revenue split, state that the fee
is included in the revenue split.

N/A

(b) If the registrant is a closed-end management investment company, describe
the services provided to the registrant by the securities lending agent in
the registrants most recent fiscal year.

N/A


ITEM 13. 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, 2019


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, 2019


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

Date August 29, 2019

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