Andre Ayew has been sold by Swansea City to West Ham for a club record fee of £20.5 million ($26.7 million).
Ayew scored 12 goals in the Premier League for Swansea last season.
The Hammers co-chairman David Gold confirmed the transfer on Twitter, writing: “Andre Morgan Ayew, also known as Dede Ayew is a Ghanaian international, joins West Ham on a four year deal.”
Ayew added on West Ham’s official website: “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.”