<SEC-DOCUMENT>0001104659-21-020608-index.html : 20210211
<SEC-HEADER>0001104659-21-020608.hdr.sgml : 20210211
<ACCEPTANCE-DATETIME>20210211151358
ACCESSION NUMBER:		0001104659-21-020608
CONFORMED SUBMISSION TYPE:	SC 13G
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20210211
DATE AS OF CHANGE:		20210211

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MERCURY SYSTEMS INC
		CENTRAL INDEX KEY:			0001049521
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRONIC COMPONENTS & ACCESSORIES [3670]
		IRS NUMBER:				042741391
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			0703

	FILING VALUES:
		FORM TYPE:		SC 13G
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-52823
		FILM NUMBER:		21619137

	BUSINESS ADDRESS:	
		STREET 1:		50 MINUTEMAN ROAD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
		BUSINESS PHONE:		9782561300

	MAIL ADDRESS:	
		STREET 1:		50 MINUTEMAN ROAD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MERCURY COMPUTER SYSTEMS INC
		DATE OF NAME CHANGE:	19971112

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC
		CENTRAL INDEX KEY:			0001644956
		IRS NUMBER:				472614791
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G

	BUSINESS ADDRESS:	
		STREET 1:		150 NORTH RIVERSIDE PLAZA
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606
		BUSINESS PHONE:		312-236-1600

	MAIL ADDRESS:	
		STREET 1:		150 NORTH RIVERSIDE PLAZA
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606
</SEC-HEADER>
<DOCUMENT>
<TYPE>SC 13G
<SEQUENCE>1
<FILENAME>tm216055-21_sc13g.htm
<DESCRIPTION>SC 13G
<TEXT>
Document 1 - file: tm216055-21_sc13g.htm

</DOCUMENT>
</SEC-DOCUMENT>