<SEC-DOCUMENT>0000950170-24-114158-index.html : 20241010
<SEC-HEADER>0000950170-24-114158.hdr.sgml : 20241010
<ACCEPTANCE-DATETIME>20241010201959
ACCESSION NUMBER:		0000950170-24-114158
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20241010
FILED AS OF DATE:		20241010
DATE AS OF CHANGE:		20241010

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Houghton Adam
		CENTRAL INDEX KEY:			0002031691
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-42366
		FILM NUMBER:		241366133

	MAIL ADDRESS:	
		STREET 1:		UPSTREAM BIO, INC.
		STREET 2:		460 TOTTEN POND ROAD, SUITE 420
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Upstream Bio, Inc.
		CENTRAL INDEX KEY:			0002022626
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		890 WINTER STREET, SUITE 200
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
		BUSINESS PHONE:		781-208-2466

	MAIL ADDRESS:	
		STREET 1:		890 WINTER STREET, SUITE 200
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>ownership.xml
<DESCRIPTION>3
<TEXT>
Document 1 - file: ownership.html

Document 1 - RAW XML: ownership.xml

</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>ck0002022626-ex24.htm
<DESCRIPTION>EX-24
<TEXT>
Document 2 - file: ck0002022626-ex24.htm

</DOCUMENT>
</SEC-DOCUMENT>