The Northern Irishman had led 7-2 going into the evening session and never looked at risk of throwing away his advantage, notching up breaks of 57 and 62 en route to glory.
Trump has been the form player in snooker this season, winning the English Open, Wuhan Open and Northern Ireland Open, but the world number two was unable to cope with the form of the world number four on the night.
It is the first title win of the season for Allen, who last won this particular event in 2020.
"I've been working so hard to get my game back," Allen told ITV Sport after sealing the victory.
The 37-year-old dedicated the win to his late coach Joe Shortt, who died earlier this year.
"Joe Shortt's not here anymore. He was a big part of my life - not just on the table but off it.
"Me and my dad have lost one of our closest friends - so that was for Joe."
Allen picks up a tidy £150,000 for winning the tournament, while Judd takes home £60,000 as the runner-up.
