Higgins was on the brink of losing with a session to spare at 14-7 behind but rallied in spectacular style at the Crucible Theatre – taking eight of the next nine frames to level the match at 15-15.
However, Williams found something deep within himself to grind out the three frames he needed to triumph 18-16 and, at 43 years old, become the oldest world champion since his fellow Welshman Ray Reardon in 1978. And true to a promise he made earlier in the tournament, the now three-time world champion conducted his post-match press conference completely naked, apart from a strategically placed Betfred towel to cover his modesty.
With Higgins being 42, the duo had the highest combined age of any two world finalists in Crucible Theatre history and the fact they both turned professional together back in 1992 only added to the intrigue – culminating in one of the most exciting, dramatic finals in recent memory.
And that provided a little solace to the Wishaw potter, although the disappointment as he finished as runner-up for the second year in a row was palpable following the defeat.
“It was an unbelievable occasion and great to be playing in front of this crowd again against an incredible player like Mark,” said a gallant Higgins.
“The red he potted in the last frame was a joke really and it was one of the best breaks I’ve ever seen under pressure to win it.
“I was 14-7 behind and I just wanted to take it to a final session – I didn’t want to lose with a session to spare.
“Luckily I did that and then tonight I came in and put a bit of pressure on Mark. It was to no avail but it must have been a good match to watch.
“Obviously I’m disappointed but every credit to him – he’s a brilliant champion.”
From 7-7, Higgins lost the final three frames of Sunday evening’s session and his poor run continued into Monday afternoon.
Williams took complete control and breaks of 61, 56, 69 and 52 helped him win all four frames before the mid-session interval – while the Scot scored just 31 points – to lead 14-7.
But Higgins ensured there wouldn’t be a final finishing with a session to spare for the first time since 1993, as a gritty run of 67 handed him frame 22 before knocks of 72 and 80 closed the gap even further, to 14-10.
Williams stopped the rot and had a healthy 15-10 advantage heading into the evening, only for Higgins to level proceedings at 15-15.
The Scot made breaks of 131, 67, 82, 52 and 62, often after the Welshman had got in first.
Having then lost eight of the previous nine frames, the world No 7 could have crumbled but instead he grittily made contributions of 41 and 33 to move back ahead at 16-15 before nervelessly edging within one of victory thanks to a break of 100.
He missed a pink to seal the title in the next, as Higgins pinched the frame with a run of 65 but Williams quickly put that out of his head and produced arguably the most important break of his career – a 69 – to seal an 18-16 win and a third world title, 15 years after his last.
l Watch the snooker World Championship live on Eurosport and Eurosport Player with Colin Murray and analysis from Ronnie O’Sullivan.