Twice during the match, Selby appeared to be cruising to a one-sided victory when he held respective leads of 5-0 and then 7-2, but the latter scoreline sparked a comeback from world number one Trump, who won five of the next six frames to cut an increasingly jittery Selby's lead to 8-7.
From there, the pair traded mistakes and frames to set up a taut finish, with Selby 9-8 ahead and only needing one frame for victory, knowing that his opponent himself only needed two.
With the stakes so high, more mistakes crept in from both camps, but it was Selby who held his nerve to win the 18th of a possible 19 frames and claim a third title to go with his victories in 2012 and 2016.
“To win another Triple Crown event - they're not easy to win, as you can tell, it took me nine years to get back here,” he told BBC Sport.
“Judd put me under pressure - I was a bit all over the place towards the end, I don't know how I managed to make it (the winning break).”
Selby was cruising at 7-2 ahead when errors started to creep into his game, opening the door for Trump to mount a comeback. The world's best player duly delivered to win the next frame, but it was the 11th that really piled the pressure on Selby.
The 42-year-old initially had his opponents on the ropes, but after a foul from Trump, Selby was awarded a free ball. In a gesture of good sportsmanship, Selby told the referee he disagreed with the decision.
Trump made a further attempt to get out of the snooker, and in doing so fluked the potting of a red ball, allowing him to go on and win a frame that took nearly 39 minutes.
As the match went deeper into the night, Trump looked increasingly likely to send it all the way, but he was ultimately unable to convert the opportunity to defend his 2024 title.
“It wasn't me playing amazing, Mark let me back in a little bit - he was brilliant at the start, and I just dragged him down at the end,” he told BBC Sport of his fightback.
“It's hard to get over the line in these finals, but I think Mark was the best player all week; he played very, very well, and he thoroughly deserved his win.
“It's been a good week, brilliant tournament, great crowd, and I look forward to coming back next year.”