Norwegian Ruud has enjoyed a stunning season, reaching two grand slam finals, and his 6-2 6-4 semi-final dismissal of Russian Rublev was impressively authoritative.
After Ruud coasted through the opening set, the occasion fell wholly flat when the 23-year-old broke serve in the first game of the second, and did so again in the third game.
Rublev sat shaking his head at his chair in the break between games, also shrugging his shoulders towards his support team and looking lost for ideas.
He only began to make an impact after slipping 4-0 behind and at 5-2 he broke Ruud's serve to give himself and the Turin crowd hope the contest could take off.
At 5-4, it was briefly tense, but Ruud served for the match for a second time and made it count, sealing victory with a brilliant backhand winner to become the first Scandinavian finalist at the season-ending event since Stefan Edberg in 1990.
Ruud will overtake Rafael Nadal and end the year at number two in the ATP rankings should he overcome Djokovic and snare the biggest title of his career.
However, he has a 0-3 career record against the Serbian superstar.
Djokovic earlier battled past Taylor Fritz by winning a pair of tight tiebreakers to earn a 7-6 (7-5) 7-6 (8-6) victory in the first semi-final.