A relieved Williams deposited the winning black in the 32nd frame at 11:50pm.
Mark Williams won an epic battle with Barry Hawkins 17-15 to clinch his place in the Betfred World Championship final, 15 years after his last appearance in the showpiece match.
Williams was World Champion in 2000 and 2003 and his remarkable return to snooker’s biggest match is the longest gap between Crucible final appearances.
On a night of high drama, both players looked edgy as a shroud of tension descended upon the Theatre of Dreams.
They came into the session with Hawkins leading two-time World Champion Williams 13-11. However, 43-year-old Williams resolutely stuck to his task and reeled the Hawk in, trailing by just one at 15-14. There was then an extraordinary 30th frame.
Hawkins had an opportunity to clinch the frame, but missed the third last red. Williams stepped up to the plate with a sublime clearance of 42 to steal, which included a phenomenal positional shot from the black to the yellow.
Welshman Williams then claimed a scrappy 31st frame to lead for the first time in the match. Both players spurned opportunities under considerable pressure in the next. Hawkins was looking to force a decider and Williams aiming to edge over the line.
They eventually came down to the final pink, with the clock just shy of midnight. Hawkins turned down a difficult shot across the top cushion. He didn’t receive another opportunity at a pot, with Williams eventually firing in a long range pink and depositing the black to seal a nerve shredding win.
Victory sees the Welshman set up a showdown with legendary 42-year-old Scot John Higgins, who has tasted World Championship glory in Sheffield on four occasions. The meeting between two of snooker’s Class of 92 will be the first ever Crucible final to be contested between two players over the age of 40.
Williams and Higgins boast a wealth of experience and honours to their names. They have 50 ranking titles between them, with Williams having won 20 and Higgins holding 30 titles. The longevity of their success can be illustrated by the fact that regardless of who is victorious on Monday evening, the winner will become the oldest World Champion since Ray Reardon in 1978.
“I’m knackered,” said Williams. “I haven’t felt that nervous since I beat Stephen Hendry on a re-spotted black in the (1998) Masters final. I was gone in the end, I couldn’t pot three balls on the trot. Luckily for me Barry was feeling the pressure. We both collapsed. It must have been great to watch, it was like two pub players trying to get over the line.
“I’m over the moon to be in the final. I got there in the end, I don’t know how. Somehow I managed to pot a really good pink. I thought I had missed the last black, but when it dropped in I was so relieved.
“My arms and legs didn’t feel like mine. I had no feeling in my arms at all. The last thing I wanted was to play another frame. The drama and the atmosphere out there was unbelievable. I forgot how good that arena is with one table, it’s been so long.
“I’ve just got to go out there and enjoy the final. Hopefully if it does go close towards the end, I won’t collapse like a cheap tent again. I’ve grown up with John, played him in all the tournaments, and now we’re in the final of the World Championship. It’s unbelievable, I can’t wait.”
Hawkins said: “The final frame was brutal, we were both twitching all over the place. I felt good at 15-14, I was in the balls and felt quite composed, but I took my eye off a red, and from then on I started twitching.
“Mark played a lot of clever shots, good safeties, and kept potting good long balls and battling away like he does. He’s a class player, one of the all-time greats.
“I’ve played pretty well for most of the tournament, and I fancied getting to the final. Tonight I let myself down a little bit.”