The five-time champion lost 13-12 to Barry Hawkins
Five-time World Champion Ronnie O'Sullivan was knocked out of the World Championships on Tuesday night after losing in the second round to Barry Hawkins.
The 40-year-old went into the final session on Tuesday evening, trailing 9-7 against Hawkins. O'Sullivan failed to take the lead in the final session but did bring the match to a final-frame decider after winning three frames in a row to tie the match 12-12.
It was the first time in 14 years that Hawkins defeated O'Sullivan in a competitive match.
O'Sullivan's loss means that eight of the top-ten seeds have been knocked out before the quarter-finals. Only former World Champions Mark Selby and John Higgins are the surviving members of the top-ten.
Higgins defeated Ricky Walden 13-8 to book his place in the last-eight against Alan McManus, and the four-time Champion is now favourite to win the tournament for the fifth time.
The quarter-finals begin on Tuesday morning when Kyren Wilson meets former World Champion Selby. In the other quarter-final Ding Junhui meets two-time champion Mark Williams.
In the afternoon session, Higgins faces McManus in the all-Scottish clash, while Hawkins meets Hong Kong's Marco Fu.