It was the first championship match in 11 years at Rotterdam to feature two unseeded players. Monfils, 32, showed no hard evidence of the left wrist injury which has bothered him all week and forced him onto a regime of pain-killers.
The world number 33 triumphed in one and three-quarter hours with four service breaks against three-time major winner Wawrinka as he claimed his first title since Doha last year. The Frenchman took the opening set with two breaks of Wawrinka, but the 33-year-old Swiss immediately returned the favour with a 6-1 second set.
In the third, Monfils broke for 2-1, taking control of his opponent's mighty backhand. The Frenchman moved to 5-2 and saved a break point a game later as he closed out victory.