Rayo Vallecano is a professional football club founded on 29 May 1924, based in the working-class Puente de Vallecas district of Madrid, Spain. Known for its deep sociocultural and barrio-local identity, the club plays its home matches at the 14,708-capacity Campo de Fútbol de Vallecas. As a classic "yo-yo club," Rayo has frequently bounced between La Liga and the Segunda División, but its most memorable European achievement came in the 2000–01 UEFA Cup, where they reached the quarter-finals before losing to eventual runners-up Alavés. They have spent 22 seasons in the top flight and are historically the third-best club in the Community of Madrid, behind only Real Madrid and Atlético Madrid. After winning the 2017–18 Segunda División title, they continued their ambitious expansion by acquiring Oklahoma City FC in 2015 to create Rayo OKC, marking the first-ever entry of a Spanish club into the American sports market, although that venture folded shortly afterward.