The second day of the Open 13 Provence saw seven first-round singles matches and one doubles match. Seventh seed Alejandro Davidovich Fokina was victorious, but sixth seed Kei Nishikori was defeated by Pierre-Hugues Herbert.
Tsonga claims first match win in a year and a half
39 year-old Lopez took the opening set behind two breaks of serve as Tsonga was yet to find his baseline game, but the three-time Marseille champion was level after securing the only break of the second set early on.
The Frenchman broke to take a 6-5 lead and on match point, fired his 19th and final ace to claim a most satisfying victory after two hours, eight minutes of play.
"This is one of the best victories of my career, because it was tough for me to play tennis. I had so much pain for so many months", he said following the match. "Today, I won one match. That was one of my goals for this week. I'm happy like a kid.
"Both of us, we are almost 80 years old together. I've known him for a long time and I have a lot of good memories with Feli. I'm really pleased that I won against him. For me, it's a good victory; he plays well indoors, he's a lefty, he's tall. I'm just happy today.
Nishikori dumped out by Herbert, Davidovich Fokina crushes Petros Tsitsipas in other action
Herbert played a flawless match to knock off sixth seed Nishikori, firing 11 aces and winning 25 of 30 first-serve points in the 70-minute encounter.
"I knew I would need to be aggressive from the start, as I knew Kei would be better than me from the baseline", he said after the match. "I cannot complain about anything today and I stuck to my game plan from the beginning to the end.
"I am very happy with the win. I kept moving forwards and didn't let him play."
Australian qualifier Matthew Ebden rallied from a set and a break down to defeat French wild card Benjamin Bonzi 3-6, 7-6 (6), 6-3 in two hours, 27 minutes. Bonzi served for the match at 5-4 in the second set.