Ronnie O'Sullivan has announced he is to end his snooker sabbatical and will defend his world title in April.
The 37-year-old pulled out of the 2012-13 season last November because of "personal issues".
O'Sullivan had until 28 February to decide if he was going to play at this year's World Championship.
"I got a bit bored," said O'Sullivan. "I needed a rest and I thought it was time to get back to what I have done for a lot of my life."
World Snooker says it is awaiting O'Sullivan's formal entry but that, as the reigning champion, he will be scheduled to play on the opening morning of the World Championship on Saturday, 20 April.
O'Sullivan added: "Three or four months ago I was sitting thinking that I would rather be losing 10-0 in Sheffield to be back playing, rather than going for lunch, dinner and chilling out.
"I had to get back to playing, winning or losing, and it shows how big a part of my life snooker is."
O'Sullivan continued: "I certainly feel refreshed. I was never out of juice. I don't find snooker hard mentally or physically.
"It is your job and you get used to it. I needed to take time out for other things.
"I knew I couldn't take too much time out. It was always in the back of my mind that I had to come back and come back with a clear head after sorting a few things out."
The four-time champion, who has battled depression in recent years, attended the Masters as a spectator in January.
O'Sullivan has provisionally dropped to 24th in the rankings but, as defending champion, he will qualify for the World Championship and be the top seed.
Barry Hearn, chairman of the World Snooker Association, described O'Sullivan's decision as "great news" for the sport.
"Ronnie's a one-off," he told BBC Radio 5 live. "There are a lot of great players out there but Ronnie brings more to the table than most of them.
"Snooker is a buzzing sport globally. If we've achieved what we've achieved in the last 12 months without Ronnie, goodness knows what we can achieve with him. He's the cream on top of the cake."
O'Sullivan suffered badly with glandular fever last year, but put that behind him at the Crucible to land his fourth World Championship title, beating Ali Carter in the final.
However, O'Sullivan has only played one match on the tour since that victory when he was beaten by lowly-ranked Simon Bedford in a Players Tour Championship event in Gloucester in September.
He then played six exhibition matches against Jimmy White around the British Isles, the last in Liverpool on 25 October, before withdrawing the next day - on doctors' advice - from the International Championship in China.
"I've potted lots of balls, but I'm match rusty," he said: "I've not played matches in tense situations and it's going to be a tough course with no practice.
"You can never replicate match situations anywhere else. This is a massive challenge but I see this as the start of a bigger picture."
BBC Sport pundit and 1997 world champion Ken Doherty said: "At the back of my mind I did think he was going to return. When you have played the game for as long as he has it is very difficult to walk away.
"It is great news. It is great for snooker. He is our talisman. The game is not about one player but he is probably the most talented player to lift a cue. He creates a buzz.
"It is going to be difficult for him. He is going to have to knuckle down and get some quality players to face in practice. But a lot of those will not want to play him as they would rather catch him cold at the World Championship."
Another former world champion, the 2010 winner Neil Robertson of Australia, said on Twitter: "Great to see Ronnie back to defend his world title, would have been weird not to have the defending champion there."