Óscar Gutiérrez Rubio (born December 11, 1974), better known by his ring name Rey Mysterio, is an American professional wrestler most known for his tenure with WWE. He is also the general manager of Lucha Libre AAA Worldwide. Widely regarded as both one of the greatest luchadors and cruiserweight wrestlers of all time, Mysterio is an inductee of the AAA Hall of Fame, Wrestling Observer Newsletter Hall of Fame, and WWE Hall of Fame.

The nephew and trainee of Rey Misterio, Mysterio began wrestling on the independent circuit in 1989 at the age of 14 before joining Asistencia Asesoría y Administración in 1992. After brief stints with Extreme Championship Wrestling and Wrestle Association R, Mysterio signed with World Championship Wrestling (WCW) in 1996. In WCW, Mysterio helped popularize lucha libre in the United States, which led to the rise of cruiserweight wrestling divisions, winning the WCW Cruiserweight Championship five times; the WCW World Tag Team Championship three times; and the WCW Cruiserweight Tag Team Championship once. Following the closure of WCW in 2001, Mysterio wrestled for promotions including Consejo Mundial de Lucha Libre, the World Wrestling Council, and the X Wrestling Federation before joining World Wrestling Entertainment (WWE) in 2002. He stayed with WWE until 2015, winning the World Heavyweight Championship twice, the WWE Championship once, the WWE Cruiserweight Championship three times, the WWE Intercontinental Championship twice, the WWE United States Championship three times, and the WWE Tag Team Championship four times, as well as winning the 2006 Royal Rumble.