West Ham have completed the signing of left-back Arthur Masuaku from Olympiakos for a fee Sky sources understand to be £6m.
The 22-year-old Frenchman has signed a four-year contract and could make his debut in the Monday Night Football clash against Chelsea, live on Sky Sports 1 HD from 7pm.
Slaven Bilic has been looking to strengthen his options at left-back after first-choice Aaron Cresswell was ruled out for up to four months in July with a knee ligament injury.
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"It's a big honour for me to be part of this club," Masuaku told the club's website. "I was speaking with my agent about some opportunities, but when he told me about West Ham and also the coach, I didn't think twice, so in my mind, it was West Ham.
"Now, to be able to play with players like Dimitri Payet, I was thinking on the way here, it's going to be crazy. I can't wait to play with him and also all the rest of the team.
"For me, the Premier League is the biggest league in the world. When I was 18, my target was to come here, so now I am here, I have to prove myself to the fans and to the team so that I can play for this big club."
Masuaku, capped by France at U18 and U19 level, started his career with French Ligue 1 side Valenciennes before joining Olympiakos in 2014.
He has since made 74 appearances for Olympiakos, helping them win the Greek Superleague twice and the Greek Cup.
Masuaku becomes West Ham's eighth signing of the summer following the additions of Sofiane Feghouli, Toni Martinez, Harvard Nordveit, Domingos Quina, Ashley Fletcher, Gokhan Tore and the permanent arrival of Manuel Lanzini.