The wrestling legend dropped his gloves, hat and trenchcoat in the middle of the ring at the end of Sunday night's WrestleMania 33.
The 52-year-old, whose real name is Mark William Calaway, lost the main event to Roman Reigns.
Fans have been paying tribute to him with the hashtag #ThankYouTaker and #WrestleMania has been trending.
Throughout his career, the Undertaker's been a multiple world heavyweight champion, a six-time tag team titleholder and a Royal Rumble winner.
