O'Sullivan, who was aiming for a record ninth title in this event, was competing in his first UK tournament since his defeat to Zhao Xintong in the World Championship semi-finals in May.

However, 'The Rocket' had a disappointing return as Zhou capitalized on a generally sloppy performance that disrupted his potting rhythm.

This loss marked O'Sullivan’s second first-round exit at the UK Championship, following his defeat to Barry Hawkins last year.

It also prolonged his wait for a ranking title, with his last victory coming at the World Grand Prix in January 2024.

The match started with two closely contested frames both won by China's Zhou despite O'Sullivan having solid leads in each.

O'Sullivan responded with breaks of 71 and 123 to level the score before the interval, seemingly gaining momentum.

The players continued to exchange frames evenly, reaching 3-3, until 27-year-old Zhou took the seventh frame and made a 125 clearance to go two frames ahead.

O'Sullivan narrowly won the ninth frame to stay in the match, but Zhou soon had another chance to seal the win.

Although O'Sullivan led in the tenth frame, he lost his advantage, allowing Zhou to come through and secure a well-earned victory.