The 28-year is an attacking midfielder who has been capped 15 times by France and has made a big impact in Ligue 1, having been born in the French island of Reunion in the Indian Ocean.
Payet created more chances than any other player in Europe’s top five leagues last season, setting up 135 opportunities for his team-mates, comfortably more than the likes of Lionel Messi, Eden Hazard and Cesc Fabregas, who all finished in the top six.
Payet told the West Ham website: “West Ham really showed me that they wanted me to come, both the joint-chairmen (David Sullivan and David Gold) and the manager (Slaven Bilic). That’s very important for me.
“I was also keen to sign up to a clear project. West Ham’s is very interesting and matches perfectly with my ambitions.
“Firstly, I spoke with the manager, who really wished for me to come here and had been watching me a lot. He made it clear that he wanted me to sign and that too was important in my choice.
“I’m an attacking footballer so for sure I like attacking football and that they’re counting on me to help achieve that gives me a sense of responsibility. The fact that I’m here is also down to that.
“I’m very happy to be here. It’s true that it’s taken a little while but that’s normal, negotiations are like that. But now that it’s done, I’m very happy.”
Payet, whose deal includes an option for a further year, becomes the third signing at Upton Park this summer after midfielder Pedro Obiang and striker Martin Samuelsen agreed terms.
The former Nantes trainee will be available to make his debut for West Ham in their home Europa League qualifying tie with Andorran side FC Lusitans next Thursday.
Marseille were reluctant to let one of their key players leave and released a lengthy statement on Thursday in which they said it was “absolutely not their intention” to sell Payet but that they were forced to accept the offer from West Ham after a dispute with the player and his agent over a new deal.