Javier Hernandez has completed his transfer from Bayer Leverkusen to West Ham in a deal worth £16million
The 29-year-old joins the Premier League club on a three-year deal after completing a medical and agreeing personal terms.
Mexico striker Hernandez scored 39 goals in two seasons with Leverkusen and becomes West Ham's fourth signing of the transfer window.
"For me, the Premier League is the best league in the world and when the opportunity came, I was desperate to sign for this club," said the forward.
"It was not a difficult decision. West Ham is an historic club, and very ambitious - this summer you can see with the players signed that they are looking to have a very good season.
#WelcomeChichaPosted by West Ham United on Monday, 24 July 2017
"I've had three fantastic years playing in Spain and Germany, but England was really the first big chapter in my career and I am so happy to be back.
"I am desperate for the season to start and to help the team achieve all their objectives."
Pablo Zabaleta, Joe Hart and Marko Arnautovic have also joined Slaven Bilic's side in the close-season.
Hernandez moved to Leverkusen from Manchester United in 2015 following a loan spell with Real Madrid.
He won the Premier League twice at United and helped them to the 2011 Champions League final, where they were beaten 3-1 by Barcelona.
Hammers co-chairman David Sullivan hailed Hernandez's prowess in front of goal, as he said: "He has a proven goalscoring record in the Premier League, La Liga and the Bundesliga, as well in the UEFA Champions League and at international level with Mexico.
"We now have some fantastic options in attacking positions and, like all West Ham fans, I am looking forward to seeing Javier score goals in a claret and blue shirt next season."