Álvaro Morata has left Chelsea and joined Atlético Madrid on an 18-month loan deal.
The striker passed a medical on Sunday before putting pen to paper on Monday.
Morata, who started his career in the Atlético academy before making his professional debut for Real, returns to the Spanish capital after two years away.
The 26-year-old has struggled in the Premier League and has failed to impress Maurizio Sarri with nine goals in 24 appearances this season.
Sharing striking duties with Olivier Giroud and Eden Hazard, the forward featured for just 165 minutes this month.
Having also spent two years with Italian giants Juventus, Morata will be hoping to rediscover his best form in LaLiga.