Mark William Calaway (born March 24, 1965) is an American professional wrestler (Professional wrestling), better known by his ring name The Undertaker. He is signed to World Wrestling Entertainment (WWE), currently wrestling on the SmackDown (WWE SmackDown) brand (WWE Brand Extension). He is currently sidelined due to injury, while his disappearance is explained on WWE programming as due to being found in a vegetative state.

Mark Calaway began his wrestling career with World Class Championship Wrestling (WCCW) in 1984. He joined World Championship Wrestling (WCW) as "Mean" Mark Callous in 1989. When WCW did not renew Calaways contract in 1990, he joined the World Wrestling Federation (which later became World Wrestling Entertainment in 2002) as The Undertaker in November of that year. Having remained with that company ever since, Calaway is currently the only full-time wrestler that made an appearance in the very first episode of Monday Night Raw (WWE Raw), who is still with the company today.

The Undertaker has two contrasting gimmick (Glossary of professional wrestling terms#Gimmicks)s: the Deadman and the American Bad Ass. The specialty matches connected to The Undertaker (or more specifically, his "Deadman" persona) are the Casket match, the Buried Alive match, the notorious Hell in a Cell, and the Last Ride match. The Undertakers kayfabe half-brother is Kane (Glenn Jacobs), whom he has teamed up with as the Brothers of Destruction. The Undertaker is undefeated at WrestleMania with an 18-0 record, which is the single longest undefeated Wrestlemania streak in WWE history. Calaway is an eight-time world champion (World Heavyweight Championship (professional wrestling)): a four-time (List of WWE Champions) WWF/E Champion (WWE Championship) and three-time (List of World Heavyweight Champions (WWE)) World Heavyweight Champion (World Heavyweight Championship (WWE)) as The Undertaker, and a one-time (USWA Unified World Heavyweight Championship#Title history) USWA Unified World Heavyweight Champion (USWA Unified World Heavyweight Championship) as Master of Pain. The Undertaker is also a one-time (List of WWE Hardcore Champions) WWF Hardcore champion (WWE Hardcore Championship), and a seven-time world tag team champion (World Tag Team Championship): a six-time (List of World Tag Team Champions (WWE)) WWF World Tag Team Champion (World Tag Team Championship (WWE)), and one-time (List of WCW World Tag Team Champions) WCW World Tag Team Champion (WCW World Tag Team Championship). The Undertaker was the winner of the 2007 Royal Rumble (Royal Rumble (2007)) and became the first man to win the Rumble at number 30.