1975: Born Wordsley, West Midlands, December 5.
1987: Wins his first pro-am tournament at the age of 12.
1991: Scores his first 147 aged 15.
1992: Turns professional.
1993: Becomes youngest winner of ranking tournament at 17, beating Stephen Hendry to win UK Championship.
1994: Wins British Open.
1995: Wins the Masters.
1996: Wins Asian Classic and German Open. Found guilty by snooker's governing body of assaulting an official at the World Championship and handed a two-year suspended sentence, a £20,000 fine and advised to donate £10,000 to charity.
1997: Wins UK Championship for second time. Compiles the fastest 147 on record in just five minutes 20 seconds during World Championship win over Mick Price.
1998: Wins Scottish Masters. Tests positive for marijuana after winning the Irish Masters and is later stripped of the title.
2001: Wins Champions Cup, Masters, China Open, Irish Masters and his first World Championship - beating John Higgins 18-14 - before crushing Ken Doherty 10-1 in UK Championship final in York.
2004: May - Beats Graeme Dott 18-8 at the Crucible to take second World Championship.
2005: After winning the Masters, Welsh Open and Irish Masters, fails to defend his World Championship title when losing to Peter Ebdon in quarter-finals after being 8-2 ahead. Claims in his post-match press conference that he will take a year off from the sport. But he plays in every tournament of the 2005-06 campaign except the Malta Cup.
December - Loses 9-8 to Mark King in first round of the UK Championship, sitting with a towel on his head while his opponent is at the table.
2006: April - Loses 17-11 to eventual champion Graeme Dott in World Championship semi-finals and hands his cue to a member of the audience straight afterwards.
December 14 - Walks out of his UK Championship quarter-final with Hendry in York mid-frame when 4-1 down. He is later fined £20,000 and docked 900 ranking points.
2008: March - In a China Open press conference, O'Sullivan makes lewd comments and brandishes a microphone suggestively. He later apologises for his behaviour but is fined and docked ranking points.
May 5 - Beats Ali Carter 18-8 to win his third World Championship.
2009: January 12 - Accuses snooker of being on a downward spiral, but wins the Masters despite smashing up his cue the day before the tournament.
September 20: Pots red against Mark King at the World Open and then asks referee Jan Verhaas what the maximum break prize is. The answer is nothing and O'Sullivan duly clears to 140 before having to be persuaded to pot the final black.
2011: August - Records the 11th 147 of his career - a snooker record - at the Paul Hunter classic.
October: Courts controversy by claiming he is being "raped" and "blackmailed" by the sport, comments which he later apologises for.
2012: May 7 - Wins his fourth World Championship title with an 18-11 win over Ali Carter at Sheffield's Crucible. Announces he is to take a break from the sport.
November 6 - Reveals he has abandoned plans to return to the snooker tour and will miss the rest of the season because of "personal issues which he needs to resolve".
2013: February 26 - Announces at a press conference that he will defend his world title in April after all.
May 1 - Reaches the semi-finals of the World Championship with a one-sided 13-4 victory over Stuart Bingham and immediately announces it could be his final appearance in the tournament as he plans to quit snooker for good.
May 7 - Wins his fifth World Championship title with an 18-12 victory over Barry Hawkins in the final.