The Spanish 23-year-old moves to Upton park after playing key role in the Italian club???s seventh-place finish in Serie A last season.
Obiang has attracted the attention of a number of clubs in Italy and Spain where he was part of the Atletico Madrid??academy system before moving to Sampdoria.
He has represented Spain at U17, U19 and U21 level but has yet to appear for the senior team, and is looking to the Premier League for experience that could help him push the incumbents.
“I???m very happy to have signed,” Obiang told the West Ham United website.
“We have been talking about this for a long time and now I???ve finally got the chance to come here. I went on holiday after the season had finished and I was looking forward to receiving that call to tell me where and when to sign for this Club.
???I???m very excited to play in the Premier League. It???s a style of football that will help me to progress as a player and as a person, so it will be very good.”??
Obiang is the first signing under new manager Slaven Bilic and the second summer signing for the club, after??Darren Randolph joined from Birmingham City. The club also confimred it intends to make??several more signings ahead of the 2015/16 season.