After being sent in to bat at the R. Premadasa Stadium in Colombo, Jaffna recovered from the early loss of Avishka Fernando (19) through a destructive 138-run partnership off just 66 balls between Mishara and Khawaja Nafay.
Nafay smashed 54 from 32 deliveries before departing, paving the way for Hridoy to continue the onslaught.
While Mishara reached his century in just 49 balls, Hridoy produced a blistering unbeaten 53 off 20 balls, striking five sixes and three fours as Jaffna finished with a daunting 242 for 2. Mishara remained unbeaten on 108 from 55 deliveries.
Chasing 243, Galle suffered an early setback when Thomas Rogers was dismissed without scoring. Bangladesh all-rounder Shakib Al Hasan proved expensive in his opening spell but struck a crucial blow by removing Chamika Karunaratne in his third over.
Ben Harper top-scored for Galle with 44, while Karunaratne made 39 from 21 balls and Dasun Shanaka added 34 off 19 deliveries. Despite the late fightback, Galle were restricted to 228, falling 14 runs short of the target.
Mohamed Shiraz starred with the ball for Jaffna, claiming three wickets, while Lizaad Williams picked up two. Shakib and Dilshan Madushanka chipped in with one wicket each.
The victory secured Jaffna's place in the LPL final, while Galle will have another opportunity to qualify through the second qualifier.
