Arsenal have allowed striker Lucas Perez to join West Ham for a reported fee of £5 million.
The Spaniard struggled to make an impact with the Gunners and spent last season on loan at Deportivo La Coruna.
"I'm very happy to be here at such an historic Club," he said. "I'm very excited, as West Ham are giving me the chance to stay in the Premier League and I'm very happy to be part of this new project.
"West Ham have great fans and play in an amazing stadium, so to sign here brings me great joy. I'm very motivated."
Perez becomes the Hammers' eighth signing of the summer.