Trump saw off the challenge of John Higgins – winning 6-3 – in the afternoon semi-final before O’Sullivan barely broke sweat in a 6-1 demolition of Joe Perry later on Saturday to set up a repeat of the 2018 final.
In a match that was billed as one of the clashes of the tournament, neither Trump nor HIggins hit top form in an encounter that lacked the expected concerted quality.
However, amongst the mediocrity, Trump produced the moment of the tournament in the eighth frame with an astonishing positional shot that saw the Bristolian screw the cue ball in and an out of baulk with a healthy helping of side to set up a frame-winning visit.
The greatest shot of all time? | Trump's moment of magic
"I don't think there's many players who would play it," said Trump after the match.
"There's a lot of players that would have put a colour safe or something. But I think it's my style, I can't go into my shell. Now and then you've got to put a colour safe but sometimes you've just got to go for it while the balls are there and make something happen."
The table had been re-covered ahead of the semi-finals and it appeared to throw both men off, but, spurred on by that moment of brilliance, Trump produced the only century of the match - a 136 - to seal progression to the final.
"The other cloth had been on six or seven days so it was wearing down and the cushions were starting to bounce a bit," Trump said afterwards.
"With the new one on, the cushions were very slow and I play with a lot of side so it was throwing off a little different.
I had to do everything simple by the end.
Trump also talked about his tiredness coming into the game and blamed it partially for his struggles.
"The crowd are the only thing keeping me going!" Trump added.
Trump's victory saw him lay in wait for O'Sullivan, who defeated Perry by six frames to one in a one-sided semi-final in the evening session.
O'Sullivan produced four breaks in excess of 50 - 58, 54, 72 and 90 - and was on for course for a whitewash with a five-frame advantage but Perry avoided that ignominy by sealing frame six courtesy of multiple visits to the table.
O’Sullivan not fussed by prospect of 37th ranking title
However, the Rocket, chasing a record 37th ranking title, produced another plus 50 run, this time 71, to seal his spot in the final.
The showdown represents a repeat of the 2018 final - won by 9-7 Trump - and offers O'Sullivan the chance to claim a record-breaking 37th ranking title.
“I am sorry to disappoint you but, you know, when you have been doing it for so long you find other things that motivate you,” said O’Sullivan on the prospect of moving past Stephen Hendry on 36 titles.
“For me, it was never about records and stuff like that. It was just about trying to enjoy the game.
If you can enjoy the game, you have more chance of longevity, you know?
Coverage of the final begins at 12:45 on Sunday on Eurosport and Eurosport Player