Williams, 50, will become the oldest ever participant in a World Championship final.
He beat Judd Trump 17-14 in the semi-final to confirm his progression, rallying back after falling to a 7-3 deficit in the early stages.
He had previously downed John Higgins by a narrow 13-12 scoreline in the quarter-finals.
Williams said he was pleasantly surprised to have reached the final: “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.”
It was an emotional win for Williams, who had been on poor form ahead of the World Championships, citing eye problems: “I really struggled with my eyes in the past couple of tournaments and I’ve tried everything – contacts, varifocals.
“I left it for Lee to decide because he knows if I’m playing alright and how I’m hitting them, and he said he thought I was better off going without them.”
Chasing a fourth title, Williams will face Zhao Xintong in the final. The Chinese phenom beat Ronnie O’Sullivan in the previous round.
What time is Mark Williams vs Zhao Xintong?
Williams and Zhao will face off at the Crucible on Sunday afternoon.
The final is a best-of-35-frames match, and is set to start at 1pm BST on Sunday May 4, 2025. If needed, the match will finish on Monday, May 5.
TV channel: In the UK, the World Snooker Championship is being broadcast live and free-to-air across the BBC. The final will be broadcast on BBC Two.
Live stream: Williams vs Zhao will be shown in full online via BBC iPlayer and the BBC Sport website.
