West Ham have signed Ivory Coast winger Maxwel Cornet from Burnley on a five-year contract for an undisclosed fee after paying his £17.5m release clause.
He was Burnley's top scorer last season with nine goals in 28 appearances as the Clarets were relegated from the Premier League.
Cornet spent seven and a half seasons at Lyon, playing 252 games and scoring 51 goals for the Ligue 1 club.
Cornet, who can play as a left-winger, wing-back or full-back, has a further one-year option on his contract.
"It's a new step for me to join this big club and I'm really happy to be here, to be part of the project for the club. I'm just excited to start," said Cornet, who has scored six goals in 29 appearances for Ivory Coast.
"Everyone knows the level here in the Premier League is very high and I want to play here for that, so I'm really happy to be here for the next stage in my career."
Cornet becomes West Ham's fifth signing of the summer after striker Gianluca Scamacca, defender Nayef Aguerd, midfielder Flynn Downes, and goalkeeper Alphonse Areola.
Hammers boss David Moyes said: "He is a versatile player with good experience, both in the Premier League and in European football, and will add strength and quality to our squad.
"He made a big impact with his performances for Burnley last season and he has impressed me with his desire to improve and challenge himself further here at West Ham."
Find all the latest football transfers on our dedicated page.
- Our coverage of West Ham United is bigger and better than ever before - here's everything you need to know to make sure you never miss a moment
- Everything Hammers - go straight to all the best content