World number six Fu was sent packing by Sheffield amateur Mitchell Travis as the youngster triumphed 6-5.
Fu led four times but Travis kept coming back and pipped the decider after an unintentional snooker.
"I haven't got words for that yet, it's the biggest win of my life," Travis, 21, told World Snooker. "Before the match I knew I had nothing to lose. I came here as a rank outsider and thought as long as I don't make myself look like a muppet, I'll enjoy it.
"I was 2-0 down and went to the toilet and just had a word with myself to just play my natural game and not to put pressure on myself, and luckily I came through.
"The venue was absolutely marvellous and it was a dream come true to play here, I'll never forget it."
Three-times UK champion John Higgins beat Alex Borg 6-2 to reach the second round.
Higgins cruised into a 4-0 lead at the interval, but Malta's Borg made a fist of it before a 101 break sealed victory for the Scot.
"Alex didn't really start well," Higgins told World Snooker afterwards. "He's not played on the big stage for a while. He got in first during the first few frames but missed a couple of balls and I did ok from there.
"There's been a lot of talk that it would be a shock if any of the top 16 lost but Marco Fu lost earlier and he's been one of the in-form players this season.
"I'm not feeling too confident at the moment. I feel like I'm beginning to hit the ball a bit better though."
Other key results were Stephen Maguire's 6-2 win over Leeds amateur Sanderson Lam, with the world number five next facing Luca Brecel, the Belgian teenager who overcame Mike Dunn 6-4.
Matthew Stevens, the 2003 champ, also progressed, as did James Wattana and Ricky Walden.
First round results - Friday sessions:
Robbie Williams 6-2 Aditya Mehta
Matthew Stevens 6 -4 Ryan Clark
James Wattana 6-2 Ian Burns
Luca Brecel 6-4 Mike Dunn
Joe Perry 6- 3 James Cahill
Daniel Wells 6-4 Alfie Burden
Stephen Maguire 6-2 Sanderson Lam
John Higgins 6-2 Alex Borg
Scott Donaldson 6-4 Matthew Selt
Rod Lawler 6-3 Thanawat Tirapongpaiboon
Mitchell Travis 6-5 Marco Fu
Kurt Maflin 6-4 Liam Highfield
Robert Milkins 6-3 Patrick Einsle
Mark Davis 6-2 Robin Hull
Ricky Walden 6-0 Cao Xin Long
Tian Pengfei 6 -1 Pankaj Advani
- Sports & Recreation
- Mitchell Travis
- Alex Borg