The Congolese defender has been an instant hit at the Boleyn since joining the club on loan on deadline-day last September.
Having appeared in almost every game this season for the Hammers, Llunga has been gathering admirers from many tops Premiership and European sides with his battling performances.
Speaking on the official site Scott Duxbury said, "Having also exercised the option to keep Herita Ilunga at the club long-term, we are very happy with the business we have done."