Three-time champion Mark Williams produced a vintage display to defeat world number one Judd Trump 17-14, becoming the oldest ever player to reach a World Championship final.
The Welshman, who turned 50 in March, eclipses his compatriot Ray Reardon, who won the title six times and appeared in the 1982 final as a 49-year-old.
Williams had trailed 7-3 early in the match but his enduring class shone through as he reined in the 2019 winner to 8-8 on Friday, then pulled clear over two sessions on Saturday to avenge his 17-16 loss to Trump in their last-four Crucible thriller in 2022.
"I was starting to twitch towards the end, I'm not going to lie. I nearly missed the black in the last frame - I did feel a bit of tension on the back arm," Williams told BBC Sport.
"I'm never normally nervous at any stage but I was in that break. I can't believe I'm in another final - I don't know how I'm doing to be honest."
Resuming 13-11 up, the Welshman took the first two frames with half centuries before Trump responded with his 106th century of a fruitful campaign, which has yielded six appearances in finals.
However, when Trump hit a safety shot too thinly, it left Williams among the balls and he capitalised with a superb 100 break of his own to lead 16-12 at the mid-session interval.
The 35-year-old Englishman, who was looking to add to his world crown from 2019, took the 29th frame and made a 116 clearance when Williams missed a red to the left middle to get back to 16-14.
His hopes of a revival were dashed when he missed a difficult black to the right corner and Williams wrapped up a famous victory with his second century of the evening.
"Mark was the more consistent player throughout and in the end he really deserved the win. There are no negatives, I tried my heart out and just ran out of steam," Trump said.
"Any other player apart from Mark and I probably would have been in the final, so I think you just have to take your hat off to him, he was too good over the three days and I'll try to improve for next year."
Williams will now face China's Zhao Xintong in the first world final to be contested by two left-handed players.
Their best-of-35 encounter will get under way on Sunday at 13:00 BST, which will be live on BBC Two.