Brecel looked like he would be in for a heavy defeat to the five-time world champion when he trailed 4-1 in the quarter-final tie in Guangzhou.
But the 22-year-old, who has only appeared in one major ranking final in his career, produced a stunning comeback winning four frames in a row against the man considered the best snooker player on the planet to win the match.
Brecel stormed back with runs of 110 and 103 to close to 4-3. He then got the better of a scrappy eighth frame to level the tie before he potted the final brown, blue and pink to score one of his career best wins.
The 2016 German Masters finalist will play China’s Li Hang in Monday’s China Championship semi-final. His superb victory against O’Sullivan means he is guaranteed prize money of at least £32,000 for reaching the semi-finals – his best ever reward in a single tournament – and stands two wins away from winning his first ever ranking event.
Brecel said. ““It was unbelievable.
“Against most players you think you can come back from 4-1 down, but against Ronnie you don’t fancy it because he is so good. When I made a century I started believing again. I kept really cool and made some good breaks.
“I’m looking forward to the semi-finals. I have felt so good this week, as if it can be my week. I am practising consistently with no days off so maybe that’s the difference.”
LUCA BRECEL – THE FACTS
Born: March 1995
Turned Professional: 2011
In 2009, he became the youngest ever winner of the European Under-19 Championship, beating Michael Wasley 6-5 in the final in St Petersburg.
Brecel also made snooker history in 2012 as he became the youngest player ever to reach the Crucible at the age of just 17.
He reached his first ever ranking event final at the 2016 German Masters, winning six matches including a 6-3 defeat of Kyren Wilson in the semi-final, before losing to Martin Gould. Brecel has also reached the final of the one-frame Shoot-Out, losing out to Robin Hull in 2016.
The Belgian looked on cards for a place in the second round of the World Championships earlier this year but Marco Fu came back from 7-2 down to win the match.
Brecel’s next opponent Li Hang also has dreams of winning his first world ranking event after he defeated world number 16 Mark Williams 5-3.
Williams started brightly taking a three frame lead before the 26-year-old fought back tremendously to secure a place in a major ranking semi-final for the first time.
The other semi-final will be a clash between two of the world’s top 16 as Shaun Murphy goes head to head with Ali Carter.
Former world champion Shaun Murphy beat China’s Zhou Yuelong – who defeated world champion Mark Selby earlier in the week – 5-2 and Carter, looking to win his third major ranking title in China, beat Irishman Fergal O’Brien by the same scoreline.