Óscar Gutiérrez (born December 11, 1974), better known by his ring names Rey Mysterio Jr, or simply Rey Mysterio, is a Mexican-American professional wrestler. He is best known for his long tenure in WWE from July 2002 to February 2015. He is also known for his work in Extreme Championship Wrestling (ECW), AAA, and World Championship Wrestling (WCW). Gutierrez was trained by his uncle Rey Misterio, Sr., learning the high-flying Lucha Libre style that has been his trademark.

“Rey Misterio” is Spanish for “King Mystery”. He subsequently dropped the “Junior” from his name when he began working for WWE in July 2002.

Mysterio is known for having a high-flying style, which helped kick-start the cruiserweight wrestling revolution in the United States in the late 1990s during his time in WCW, and is often regarded as one of the greatest high-flyers in wrestling history. In WCW, he won the WCW World Tag Team Championship three times, and the WCW Cruiserweight Tag Team Championship once with Billy Kidmanas part of The Filthy Animals. In WWE, Mysterio is a three-time world champion, having held WWE’s World Heavyweight Championship twice and the WWE Championship once. He has also held the WWE Tag Team Championship a record-tying four times, and the WWE Intercontinental Championship twice. All totaled, Mysterio has won 21 titles between WWE and WCW, including a record eight Cruiserweight Championships (five in WCW, three in WWE). He was the 21st person to complete the WWE Triple Crown, and was the winner of the 2006 Royal Rumble.