The 31-year-old had never previously finished higher than 16th in any European Tour event, but birdied four of the last five holes for a 64 and two-stroke ping i20 driver
over Italian teenager Matteo Manassero.
Challenge Tour graduate Quesne, ranked 322nd in the world, said: "I think it's the best day of my life - I will remember this day all of my life."
The eight-under-par round was the lowest of his career on the main circuit and the #139,039 first prize more than doubled his earnings since he made his debut eight years ago.
Joint sixth when he teed off, Quesne finished a front-nine 32 with back-to-back birdies, but it was the three in a row from the 14th which put him out in front.
That run was completed with a magnificent two ping i20 driver
from well over 60 feet at the long 16th, but his closing seven-footer on the difficult 18th always looked likely to give him victory.
Eighteen-year-old Manassero, who opened the tournament with a 64, took second place on his own i20 driver
when overnight leader Eduardo de la Riva bogeyed the last to drop into third place.
As is their custom, Quesne was showered with champagne by fellow French players afterwards, but at least he resisted the temptation to go and jump in the lake on the 18th.