John Higgins produced a gritty display to beat Mark Williams 17-14 and set up a mouth-watering World Championship final with Judd Trump.
Williams dominated for much of the match with three centuries but too many errors cost him dear.
Higgins clung to the Welshman's tails before edging ahead for the first time at 12-11 on Saturday morning.
Resuming 13-11 behind, Williams bagged a 105 and 92, but Higgins fired a 123 and edged two scrappy frames to win.
The final two frames were nervy affairs, with both players struggling the closer they got to the finish line, but it was an emotional Higgins who prevailed to secure his fifth world final.
"I can't believe I've won the game," the 35-year-old told BBC Sport. "We were both missing chances because it's a high-pressure situation. I knew I would miss and I was hoping he would miss.
"But it's unbelievable. It's been a long year."
Higgins, known as the Wizard of Wishaw, has won four tournaments, including the UK Championship and Welsh Open, since his return from a ban for failing to report approaches made to him about throwing frames. He also suffered the death of his father in February.
Williams and Higgins were competing in their third Crucible semi-final together, with the Welshman having prevailed in 1999 and 2000, but considering they had racked up 11 World semis between them, it was a surprisingly twitchy encounter.
It was, nonetheless, a hugely intriguing encounter between these two snooker heavyweights, despite the lack of fireworks on show in comparison to the earlier explosive semi-final between Trump and Ding Junhui.
After dishing up two centuries each in the first two sessions, it seemed Williams, eyeing a third world crown, was slowly taking control.
A 9-5 lead should have been 10-5 and, even by the battling standards of Higgins, it would have been a difficult deficit to overturn.
But the Scot nicked it and the onslaught and another famous fightback began. Higgins later admitted it had been a "major turning point".
Aided by the Williams errors, Higgins edged ahead for the first time on Saturday morning at 12-11 and then his eighth frame in 10 ensured he was in the driving seat for the last session at 13-11 up.
Despite his laid-back nature, the competitiveness and drive of Williams should not be under-estimated and he showed in the evening's opening frame just why he has risen to number one in the provisional world rankings.
With 14 reds and 13 blacks already sunk, Williams had his eyes firmly on a maximum 147 but agonisingly saw the white disappear down the hole after potting the 14th black to end on 105.
It was the start he so desperately needed, but his opponent immediately kept up the pressure to regain his two-frame advantage.
Back came Williams with a 92, although a poor positional shot denied him a go at beating the highest break of 138 to leave the frustrated Welshman swiping the air with his cue.
Higgins seemed to draw inspiration and resolve from a bizarre incident in frame 29. When starting a break, a crowd member stood up and heckled the player before being ejected by referee Eirian Williams.
The three-time world champion said after the match the incident had not put him off and in typically gritty fashion, he simply dug in and went on to produce a wonderful 123 to open up a 15-14 lead.
Again, Williams had his chances to get back into the match but his trusty left arm showed no signs of reignition and Higgins edged to within one of victory.
A run of 64 had Williams dreaming of a miraculous comeback but after three more misses, Higgins finally stepped in to finish the job off and was pointing to the sky with relief and elation.
With just the 21-year-old Trump standing in the way of a fourth world crown, Higgins said: "It will be an incredible final. He just pots and pots - even when you get the white on the cushion.
"Judd's great for the game. He's a great lad and I'm really looking forward to the final."
Williams, who can look back on a very successful season which saw him pick up the German Masters trophy, said: "I can't grumble too much. I played quite well tonight but I had one bad session.
"I had John on the rack and that might have been my best chance of winning another world title."
The final between Trump and Higgins gets under way at 1400 on Sunday.