As filed with the U.S. Securities and Exchange Commission on May 20, 2016

1933 Act File No. 333-30810

1940 Act File No. 811-09819

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	x
Post-Effective Amendment No. 220	x

and

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	x
Amendment No. 221

STATE STREET INSTITUTIONAL INVESTMENT TRUST

P.O. Box 5049, Boston, Massachusetts 02206

(Address of Principal Executive Offices)

(617) 664-7037

(Registrant’s Telephone Number)

Joshua A. Weinberg, Esq.

Vice President and Managing Counsel

SSGA Funds Management, Inc.

One Lincoln Street

Boston, MA 02111

(Name and Address of Agent for Service)

Copy to:

Timothy W. Diggins, Esq.

Ropes & Gray LLP

800 Boylston Street

Boston, Massachusetts 02199-3600

It is proposed that this filing will become effective (check appropriate box):

x Immediately upon filing pursuant to paragraph (b)

¨ On (date) pursuant to paragraph (b)

¨ 60 days after filing pursuant to paragraph (a)(1)

¨ On (date) pursuant to paragraph (a)(1) of Rule 485.

¨ 75 days after filing pursuant to paragraph (a)(2)

¨ On (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

¨ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, (the “1933 Act”), and the Investment Company Act of 1940, as amended, the Registrant, State Street Institutional Investment Trust (the “Trust”) certifies that it meets all of the requirements for effectiveness of this Amendment to the Trust’s Registration Statement under Rule 485(b) under the 1933 Act and has duly caused this Amendment to the Trust’s Registration Statement to be signed on its behalf by the undersigned, thereto duly authorized, in the City of Boston and Commonwealth of Massachusetts on this 20^th day of May, 2016.

STATE STREET INSTITUTIONAL INVESTMENT TRUST
By:	/s/ Ellen M. Needham
	Ellen M. Needham
	President

Pursuant to the requirements of the 1933 Act, as amended, this Registration Statement for the Trust has been signed below by the following persons in the capacities indicated on the 20^th day of May, 2016:

Signature	Signature
/s/ William L. Boyan* William L. Boyan, Trustee	/s/ James E. Ross* James E. Ross, Trustee
/s/ Michael F. Holland*	/s/ Richard D. Shirk*
Michael F. Holland, Trustee	Richard D. Shirk, Trustee
/s/ William L. Marshall* William L. Marshall, Trustee	/s/ Rina K. Spence* Rina K. Spence, Trustee
/s/ Patrick J. Riley* Patrick J. Riley, Trustee	/s/ Bruce D. Taber* Bruce D. Taber, Trustee
/s/ Bruce S. Rosenberg Bruce S. Rosenberg, Treasurer and Principal Financial Officer	/s/ Douglas T. Williams* Douglas T. Williams, Trustee
/s/ Ellen M. Needham Ellen M. Needham, President and Principal Executive Officer
/s/ Kristin Schantz *By: Kristin Schantz Attorney-in-Fact Pursuant to Powers of Attorney

SIGNATURES

This Registration Statement contains certain disclosures regarding the State Street International Developed Equity Index Portfolio, State Street Money Market Portfolio, State Street U.S. Government Money Market Portfolio, State Street Treasury Money Market Portfolio and State Street Treasury Plus Money Market Portfolio (the “Portfolios”), series of State Street Master Funds (the “Trust”). The Trust has, subject to the next following sentence, duly caused this Post-Effective Amendment No. 220 to the Registration Statement on Form N-1A of State Street Institutional Investment Trust (the “Registrant”) to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston and the Commonwealth of Massachusetts on May 20, 2016. The Trust is executing this Registration Statement only in respect of the disclosures contained herein specifically describing the Trust and the Portfolios, and hereby disclaims any responsibility or liability as to any other disclosures in this Registration Statement.

STATE STREET MASTER FUNDS
By:	/s/ Ellen M. Needham
	Ellen M. Needham
	President, State Street Master Funds

This Registration Statement on Form N-1A of the Registrant has been signed below by the following persons, solely in the capacities indicated and subject to the next following sentence, on May 20, 2016. Each of the following persons is signing this Post-Effective Amendment No. 220 to this Registration Statement only in respect of the disclosures contained herein specifically describing the Trust and the Portfolios, and hereby disclaims any responsibility or liability as to any other disclosures in this Registration Statement.

Signature	Signature
/s/ William L. Boyan*	/s/ James E. Ross*
William L. Boyan, Trustee	James E. Ross, Trustee
/s/ Michael F. Holland*	/s/ Richard D. Shirk*
Michael F. Holland, Trustee	Richard D. Shirk, Trustee
/s/ William L. Marshall*	/s/ Rina K. Spence*
William L. Marshall, Trustee	Rina K. Spence, Trustee
/s/ Patrick J. Riley*	/s/ Bruce D. Taber*
Patrick J. Riley, Trustee	Bruce D. Taber, Trustee
/s/ Bruce S. Rosenberg	/s/ Douglas T. Williams*
Bruce S. Rosenberg, Treasurer and Principal Financial Officer	Douglas T. Williams, Trustee
/s/ Ellen M. Needham
Ellen M. Needham, President and Principal Executive Officer

/s/ Kristin Schantz

*By: Kristin Schantz

Attorney-in-Fact

Pursuant to Powers of Attorney

SIGNATURES

This Registration Statement contains certain disclosures regarding the State Street Clarion Global Infrastructure & MLP Portfolio and State Street Disciplined Global Equity Portfolio (the “Portfolios”), series of SSGA Active Trust (the “Trust”). The Trust has, subject to the next following sentence, duly caused this Post-Effective Amendment No. 220 to the Registration Statement on Form N- 1A of State Street Institutional Investment Trust (the “Registrant”) to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston and the Commonwealth of Massachusetts on May 20, 2016. The Trust is executing this Registration Statement only in respect of the disclosures contained herein specifically describing the Trust and the Portfolios, and hereby disclaims any responsibility or liability as to any other disclosures in this Registration Statement.

	SSGA Active Trust
By:	/s/ Ellen M. Needham
	Ellen M. Needham
	President

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, this Amendment to the Registration Statement has been signed below by the following persons in the capacities and on the date indicated: Each of the following persons is signing this Amendment to the Registration Statement only in respect of the disclosures contained herein specifically describing the Trust and the Portfolio, and hereby disclaims any responsibility or liability as to any other disclosures in this Registration Statement.

SIGNATURES	TITLE	DATE
/s/ Bonny E. Boatman*	Trustee	May 20, 2016
Bonny E. Boatman
/s/ Dwight D. Churchill*	Trustee	May 20, 2016
Dwight D. Churchill
/s/ David M. Kelly*	Trustee	May 20, 2016
David M. Kelly
/s/ Frank Nesvet*	Trustee	May 20, 2016
Frank Nesvet
/s/ Carl G. Verboncoeur*	Trustee	May 20, 2016
Carl G. Verboncoeur
/s/ James E. Ross*	Trustee	May 20, 2016
James E. Ross
/s/ Ellen M. Needham	President and Principal Executive Officer	May 20, 2016
Ellen M. Needham
/s/ Bruce S. Rosenberg	Treasurer and Principal Financial Officer	May 20, 2016
Bruce S. Rosenberg

*By:	/s/ Christopher A. Madden
	Christopher A. Madden
	As Attorney-in-Fact
	Pursuant to Power of Attorney

Exhibit Index

Exhibit No.
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase