The Spanish shot-stopper only made his senior debut last season but was in fine form as the Andalusians clinched Europa League qualification after finishing seventh in La Liga
West Ham have signed goalkeeper Adrian from Betis on a free transfer.
Adrian joined the Liga club's youth ranks in 1998 and played for the B team between 2006 and 2012, but only made his senior debut last season.
West Ham are 9/1 with Coral to be relegated next season
"I am extremely happy and ecstatic to have joined such a legendary and historical club in both London and in England," he told the club's official website. "I am really looking forward to being able to kick-off my career in the best league in the world with West Ham.
"I started off my career as a 10-year-old and have been there all of my life. I came through the ranks and I made my first-team debut in the sixth league game of last season against Malaga and was an ever-present since.
"For me, the icing on the cake was helping the team to qualify for the Europa League. Achieving this qualification was a massive farewell gift for the Betis fans."