West Ham United have signed Portugal international Joao Mario on loan from Inter Milan until the end of the season.
On Thursday, the midfielder had a medical in London ahead of the deal being concluded.
Announcing the move on their official website, West Ham said Joao Mario had been named in the squad for Saturday's FA Cup fourth-round tie at League One Wigan.
The player, who will wear the No. 18 shirt, said: "I am really happy to be here.
"It's a really amazing experience to join this amazing team and I am just glad to be here.
"It was a fast move. I have spoken with everyone around the team and, for me, it is exciting to play in the Premier League."
Joao Mario, who becomes West Ham's first signing of the January window, added: "It's a really historic club with an amazing stadium and amazing players.
"I am just trying to know a little bit more about the club every day, and now I have some time to know more."