The 55-year-old, whose real name is Mark Calaway, said in a recent documentary that there was "nothing left for [him] to conquer" according to the BBC.
His words suggest plans to retire after a career spanning three decades.
But neither Mr Calaway nor the WWE have formally announced his retirement from the league.
The Dead Man, as he is nicknamed, made the comments during the new WWE biopic The Last Ride.
He spoke about his most recent match against wrestler AJ Styles, which ended with him burying his opponent and riding away on a motorcycle.
"It was a perfect moment. You don't necessarily always get those. If there was ever a perfect ending to a career, that right there was it," Mr Calaway said.
"It's time this cowboy really rides away," he added. "I can do more good outside the ring than I can inside. I'm finally at a place where I can accept that."
He said he would consider returning for one last match, but that "only time would tell".
Mr Calaway has been a multiple world heavyweight champion, six-time tag team title holder and winner of the Royal Rumble.
He began his career with World Class Championship Wrestling in 1987, and moved to the WWE in the 1990s as a final member of Ted DiBiase's Million Dollar Team.
Mr Calaway is also known as a WWE pioneer. He was part of the first Casket Match at Survivor Series in 1992, the first Buried Alive match in 1996 and the inaugural Hell in a Cell match in 1997.
Despite enormous popularity, however, he has not chosen to follow superstars like John Cena or Dwayne "The Rock" Johnson into movies.
He told the BBC last month that he "had opportunities to do so" but had decided against it.
"It doesn't work for me," said Mr Calaway. "Wresting and WWE is my passion. It's where I've completely invested and where my heart is at."
On Sunday, he tweeted a clip from The Last Ride and wrote "you can never appreciate how long the road was until you've driven to the end".
His revelation has prompted a wave of supportive messages on social media, using the hashtag #ThankYouTaker. AJ Styles said he would be "honoured" if their fight had been The Undertaker's last.