West Ham have signed Manchester United midfielder Jesse Lingard on loan until the end of the season, after completing the permanent signing of Said Benrahma.
England international Lingard, who has scored 33 goals in 210 appearances for United, had played just three times for the club this season.
United manager Ole Gunnar Solskjaer said he wanted the 28-year-old to return to Old Trafford "revitalised".
"I'm excited," said Lingard. "It's another new chapter in my life."
He added: "Nothing is guaranteed but I've come here to work hard and help the team and bring my experience. That's the main aim. I just want to enjoy my football and get back playing again and get my feet back on the pitch."
The Hammers were due to make winger Benrahma's loan move from Brentford permanent in the summer but they finalised the deal worth up to £30m earlier on Friday to free up loan space.
Premier League clubs can only have two domestic loan signings; West Ham also have Craig Dawson on loan from Watford.
Algeria international Benrahma moved to London Stadium on loan from Championship side Brentford in October, in an agreement that obliged the Hammers to make a permanent transfer, worth £25m plus £5m in add-ons, at the end of this season - but now the 25-year-old has signed a contract until 2026.
Lingard reunites with former Manchester United manager David Moyes at West Ham.
"There were lots of clubs involved but, for me personally, I felt this was the right move," said Lingard.
"I've obviously had a previous relationship with the manager as he was at Man U and I've played under him before, so he knows my qualities and what I can bring to the team.
"It's important that a player and manager have a good relationship. He's got really good morals, he gets his team working hard and I've had a chat with him already and there are no guarantees - it's down to me to put the work in and put the graft in, to get into the team and play well week-in, week-out."
Moyes said: "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. He's played for England as a number 10, he's played for England as a number eight, and I actually think if we needed him as a false nine, 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."
Speaking at a news conference before United's Premier League match with Arsenal on Saturday (17:30 GMT), Solskjaer said Lingard had a future at the club.
"We want Jesse to come back here revitalised," he said. "We've had little to no injuries and he's not forced his way into the team, unfortunately.
"I just want him to go there and enjoy himself, show how good a player he is and come back. He is a Manchester United player through and through."
Lingard will not feature in the Hammers' home game against Liverpool on Sunday (16:30 GMT) and will be ineligible to play against his parent club in the FA Cup fifth round.
Find all the latest football transfers on our dedicated page.
- West Brom take on Fulham in a relegation battle live this Saturday: Find out all ways you can watch that and more televised fixtures here