Williams was beaten in the 1998 German final by John Parrott
Mark Williams will face Mark Selby in Sunday's final of the German Masters.
Wales's Williams notched a 6-3 victory over Marco Fu in the semi-finals, while Selby overcame Graeme Dott 6-4.
World number three Williams led 3-1 and, after Fu had levelled at 3-3, eventually saw off the Hong Kong cueman in just under two hours.
Selby fought his way back from 3-1 down against Scot Dott, before reeling off three frames in a row to reach the best-of-17 decider in Berlin.
"I've got to know Mark very well over the last year or so and we've become good friends so the banter in the final will be good," said Selby, looking ahead to Sunday's clash.
"He's in great form too, arguably back to his peak so it's going to be a cracker."
Williams and Fu had reached the semis on the back of impressive 5-1 wins over Joe Perry and Joe Swail respectively.
And both began their semi-final encounter fluidly - Hong Kong cueman Fu countering the 35-year-old's 56 with a visit of 60 to edge the opener.
But Williams squared it with a run of 59 and was two frames ahead thanks to runs of 46 and 49.
At 3-3, it looked the match might develop into a war of attrition, however, Williams found his rhythm once more to advance.
"It's taken me a couple of years to get back to making big finals really - it's amazing what a bit of confidence can do for you," reflected Williams, who will be at number two in the new world rankings.
"I don't think it's realistic to say that I can get back to the form of my mid-20s as that was 10 years ago, but I am playing well."
Selby, on the other hand, admitted he was struggling with his game, despite his victory.
"The balls seemed to move themselves into tricky situations in every frame and there was a lot of scrappy stuff," reflected the Leicester man after his tussle with Dott lasted three hours and 38 minutes.
Tenth-ranked Dott, who had ousted compatriot Stephen Maguire 5-2 in his quarter-final, raced into a 3-1 advantage with visits of 83, 66 and 75.
Selby clawed his way back to level terms but, 2006 world champion Dott regained the lead with a 71 in the seventh.
It was all-square again when Selby, a 5-1 conqueror of Ding Junhui 5-1 in the last eight, knocked in a break of 57.
Selby took the scrappy ninth before a 61 set him up to clinch the match.
The German Masters, first staged in 1995, has returned to snooker's list of ranking tournaments this season.