The England international has been on the fringes at Old Trafford this season and has moved to the London Stadium in search for regular first team football.
Lingard graduated from the Manchester United academy and has been with the first team since the 2011-2012 season, racking up over 200 appearances for the Red Devils in all competitions, scoring 33 goals and providing 20 assists.
His promising career has taken a nose dive in recent years and found opportunities hard to come by due to the increased competition for places at Old Trafford.
Lingard is yet to feature in the Premier League this season, and a move to East London could salvage his career.
“I’ve seen him play as a young boy, when he was still a wide player on the right, and I’ve seen him play off the left,” said David Moyes after the Hammers confirmed the signing of Lingard.
“He’s played for England as a number 10, he’s played for England as a number 8, and I actually think if we needed him as a False 9, he could do that as well.
“We’re bringing in that versatility, I’ve wanted to try to get an energetic team at the moment and Jesse has been known for his work-rate and effort, so I think he’ll fit in nicely with what we’ve got.
“I hope he brings us a little bit of quality too, and a winning mentality from Manchester United.”