After agreeing to pay Swansea £20.5m for Andre Ayew last week, West Ham have completed the signing of the Ghanaian player for a club record fee.
He signed a three-year deal with a two-year option and becomes the club’s ninth summer signing.
The fee is £20.5m, according to West Ham’s co-chairman David Gold, eclipsing the £15m the club paid Liverpool for Andy Carroll.
“I am very proud and happy to be at this magnificent club. I am happy to be playing for these fans and I hope to make the people very happy here.
“The club have a lot of ambition and have a great manager. They want to become a bigger club every year and with the new stadium and a new training ground you can feel they are moving onto another level and I want to be part of this project.
“I want to train hard, do my job and show that I deserve to play for West Ham United. I want to give back to the manager and the fans the confidence they are showing me,” he told the West Ham website.