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.
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.
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.
Earlier on Saturday, fans were refused refunds for what was meant to be the fourth session of the semi-final between Ronnie O'Sullivan and Zhao Xintong.
Zhao's 17-7 victory over the 'Rocket' was delivered with a session to spare, meaning there was no competitive action in the afternoon at the Crucible.
An exhibition featuring Steve Davis and Dennis Taylor - 40 years on from Taylor's victory in their famous black-ball final - was instead provided, along with a question-and-answer session with seven-time winner Stephen Hendry and 1997 champion Ken Doherty.
The World Snooker Tour (WST) said its box office terms and conditions mean it is "unable to offer ticket refunds or exchanges".
Ticket prices for the session, including fees, ranged from £121 to £660.
WST said: "This is the first time in over a decade that a semi-final has finished a session early, so it is a very rare occurrence and unfortunately beyond our control."