In one of the matches of the season, O’Sullivan triumphed 62-60 in a thrilling deciding frame after Trump had taken a 50-0 lead.
O’Sullivan was called for a foul as he looked to reduce the deficit, and then fluked the pink when returning to the table, only to let Trump back in with a chance of seeing it off.
But Trump then missed the yellow when 25 points ahead, with O’Sullivan mopping up and holding his nerve to win on the final black along the cushion in Llandudno.
The Rocket, who is on course to become the world number one if he wins in Wales, will face the winner of either Mark Allen or Neil Robertson in this weekend's final.
Trump, 29, on the back of runs of 54, 66, 69 and 50 took a 6-2 advantage to the interval but O’Sullivan returned for the evening session reinvigorated.
The five-time world champion, who had made runs of 64 and 100 in an inconsistent afternoon session, produced some masterful snooker in the evening session with runs of 82, 50, 130 and 134 levelling the semi-final at eight frames each.
Trump then moved within one frame of victory as he looked to beat O’Sullivan for the third time in a row.
But O’Sullivan rallied once more, taking the match to a decider after winning the penultimate frame 64-39, and then edging Trump in a nail-biting finale.
O’Sullivan, who has already won the UK Championship, Players Championship, Shanghai Masters and Champion of Champions this season, is aiming for a record-equalling 36th ranking title win.
A win at the Players Tour Championship would also see the five-time champion return to the top of the world rankings for the first time since 2010.