Argentine striker Jonathan Calleri has completed a season-long loan move to West Ham from Uruguyan club Deportivo Maldonado.
The 22-year-old linked up with his new team-mates at training on Tuesday and will go straight into the squad for Thursday's Europa League play-off first leg with Astra Giurgiu in Romania.
The forward topped the 2015 Copa Libertadores scoring charts with Sao Paulo, and has also enjoyed a fruitful stint at Boca Juniors.
"I am very happy to have signed for West Ham," Calleri told West Ham's official club website.
"This represents a fantastic new challenge for me and I am really looking forward to it.
"The Premier League is the best league in the world and so I am delighted to have this opportunity to play in such a prestigious league."
Calleri's arrival will offset the thigh injury suffered by club-record signing Andre Ayew in Monday night's 2-1 Premier League defeat at Chelsea.
The Hammers' £20.5million man Ayew trudged off after little more than half an hour, leaving manager Slaven Bilic admitting the striker will face scans to determine the extent of the injury.
While West Ham are likely to continue the search for another more established forward, Calleri's presence will certainly ease Bilic's striking options, with Sofiane Feghouli still battling a hamstring problem.
Argentina Under-23 cap Calleri moves to West Ham after representing his country at the Rio Olympics.
With 39 goals in 90 appearances in the last two seasons, Calleri is intent on warming to the challenges of English football as quickly as possible.
"It is a new chapter for me and so I am excited to get started here and to fit in as quickly as possible, so that I can be as useful as possible to my new team-mates and manager," said Calleri.
"These are exciting times for me personally and I am motivated to adapt my game to this new environment.
"I am a player who always tries to work as hard as I can and to do my best for the team."