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Mark Allen Reaches the Masters Semi-Finals after knocking out Neil Robertson
Allen, who beat Ronnie O'Sullivan, flew out of the blocks with breaks of 63 and 69 to lead 2-0, but the Australian hit back to win three successive frames.
Robertson stayed in control with a 71 to lead 4-3 but breaks of 57, 75 and a 69 steered Allen over the line.
Allen plays the winner of the later tie between Peter Ebdon and Marco Fu.
It was another phenomenal performance from Allen after the 24-year-old dumped out former number one O'Sullivan in the first round.
And as well as making his first Masters semi-final, he is the first Northern Irish player to reach the last-four in this tournament since Dennis Taylor 24 years ago.
Being the only player in the top eight left in the tournament, the pressure was on Robertson and the Melbourne left-hander began in shaky fashion and Allen needed no second invitation to pounce after a sloppy safety.
A 63 from Allen helped him take the opener, before he finally came through a fascinating 29-minute second frame with a 69.
More errors followed for Robertson in the third but a fabulous 10-foot red put the flow back into his cueing left-arm and a breathtaking 69 soon followed, which included a doubled red and two cute nudges to release a blue and red off the cushion.
With the early jitters gone, Robertson swiftly levelled the match at 2-2 with a 56 and secured his third frame on the bounce with a cool 50.
Cheered on by his noisy faithful fans from County Antrim, Allen stopped the rot to level the scores again thanks to a steady 46, only to return to his chair and watch his opponent regain the lead with a brilliant 71.
Most of the enthralled Wembley audience may have expected Robertson to power on after witnessing the way he sunk an early red with a devastating exhibition of screw from 10 feet, but his early wobbles returned and Allen was not afraid to wrestle back the initiative.
A hard-earned 57 points followed and the baize big-hitters were locked at 4-4. But the best was still to come for Allen as he racked up a run of 75 to sniff victory.
Robertson looked stunned as he continued to remain in his chair with his opponent knocking in a 69 and despite a scrappy battle over the last six reds, it was a grinning Allen who left the packed arena having secured his sixth major semi-final.
"It was close all the way and I was happy with the way I was playing but all credit to Mark," said Robertson.
"He stayed in there and never went away. Every time he got a chance he scored heavily.
"It was a hard fought match and was top standard all the way through."
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Northern Ireland's Mark Allen produced another shock at the Masters with a 6-4 win over world champion Neil Robertson to reach the semi-finals.