The Hammers have secured the 24-year old Senegalese striker on a four-year deal for an undisclosed fee, believed to be around £4.5million.
"This is a proud day to have signed for West Ham, I really love English football and I've dreamed of coming to play for one of the big English clubs. Today, West Ham have given me that opportunity and I didn't hesitate to grab it," Sakho told West Ham's official website.
"I'm looking forward to playing. It's more than a month now that I've been training for this and right now I think I'd be ready to pull on the club colours.
"I've come here to continue as I was at Metz. I'm going to give it my all, going flat out on the pitch and I think the fans will appreciate that."
West Ham United FC (@whufc_official) August 14, 2014
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