LIMITED POWER OF ATTORNEY

The undersigned hereby constitutes and appoints each of Jason F. Cole, Kory
Wentworth, and Helen Fu, and each of them individually, and with full power of
substitution, the undersigned's true and lawful attorney-in-fact to:

(1) Complete and execute for and on behalf of the undersigned, in the
undersigned's capacity as an officer, director and/or ten percent (10%)
shareholder of bluebird bio, Inc., a Delaware corporation (the "Company") any
and all instruments, certificates and documents required to be executed on
behalf of the undersigned as an individual or on behalf of the undersigned's
company or partnership, as the case may be, pursuant to Section 13 and Section
16 of the Securities Exchange Act of 1934, as amended (the "Exchange Act") or
the rules and regulations thereunder;

(2) Do and perform any and all acts for and on behalf of the undersigned which
may be necessary or desirable to complete and execute any such instruments,
certificates or documents required to be filed pursuant to Sections 13 and 16 of
the Exchange Act or the rules or regulations thereunder and timely file such
forms with the United States Securities and Exchange Commission and any stock
exchange or similar authority; and

(3) Take any other action of any type whatsoever in connection with the
foregoing which, in the opinion of such attorney-in-fact, may be of benefit to,
in the best interest of, or legally required by, the undersigned, it being
understood that the documents executed by any such attorney-in-fact on behalf of
the undersigned pursuant to this Power of Attorney shall be in such form and
shall contain such terms and conditions as such attorney-in-fact may approve in
such attorney-in-fact's discretion.

The undersigned hereby grants to each such attorney-in-fact, acting singly, full
power and authority to do and perform any and every act which is necessary,
proper or desirable to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that any such attorney-in-fact, or any such
attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this Power of Attorney and the rights and powers herein
granted.

The undersigned acknowledges that each of the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming,
nor is the Company assuming, any of the undersigned's responsibilities to comply
with Section 13 or Section 16 of the Exchange Act or the rules or regulations
thereunder. The undersigned hereby agrees to indemnify each attorney-in-fact and
the Company from and against any demand, damage, loss, cost or expense arising
from any false or misleading information provided by the undersigned to such
attorney-in fact.

This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file any instruments, certificates and
documents pursuant to Section 13 and 16 of the Exchange Act or the rules or
regulations thereunder with respect to the undersigned's holdings of and
transactions in securities issued by the Company, unless earlier revoked by the
undersigned in a signed writing delivered to the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of September 25, 2019.




                                         /s/ William R. Sellers
                                         William R. Sellers