Reigning champion Shaun Murphy and current UK title holder Mark Selby were both eliminated on a thrilling opening day of the Masters at London's Alexandra Palace.
Murphy lost 6-2 to China's Wu Yize in the first round, before Selby, who won the UK Championship last month, was defeated by the same score against another Chinese debutant, Xiao Guodong.
Murphy lost the opening three frames and, despite taking frame four, then lost the fifth on a black-ball finish.
Wu, 22, is ranked 13th in the world and picked up his first ranking title in November when he won the International Championship in Yanjing in his home country, beating world champions Judd Trump, Zhao Xintong and John Higgins along the way.
On his Alexandra Palace debut, Wu made a superb clearance of 137 in frame two and a break of 56 in frame seven.
"I felt a bit of pressure when I entered the stadium because it was the first time I've played in such a big stadium and the fans were so enthusiastic," said Wu.
"After the first frame, I felt a bit more relaxed and I totally enjoyed the atmosphere. It's definitely a great achievement for myself - my first time playing at the Masters and the first time beating Shaun Murphy."
For 43-year-old Murphy, who reached the semi-final of the UK Championship last month, it was a disappointing afternoon with him failing to register a single break of 50.
"I've been looking forward to today for a year, walking out as champion, but I enjoyed the first 10 minutes," said Murphy, who beat Kyren Wilson to win the Triple Crown event for a second time a year ago.
"I'm very disappointed. None of it was there. I felt everything I touched was not there. I've been working very hard, practising hard, playing a lot of snooker, so I didn't expect to play like that and I'm as shocked as anyone.
"I didn't play well, certainly the worst performance of my season, maybe the worst in the Masters.
"Wu looked calm, looked at ease and fully deserved his win. He will be a handful for anyone he plays."