Nadal played his best tennis of the week and ended Tsonga's hopes of qualifying for the eight-man ATP World Tour Finals in London.
"It was a very important victory for me," Nadal said. "It's probably the first big victory after I came back from injury."
Gael Monfils gave French fans hope of a home champion by reaching his first Paris semifinal with a 3-6, 6-4, 6-4 victory over Marin Cilic of Croatia. Monfils will play former finalist Radek Stepanek, who advanced when U.S. Open champion Juan Martin del Potro retired trailing 4-0 with a groin injury from his previous match.
Nadal returned to competition in October after a month off because of a pulled stomach muscle.
The third-seeded Djokovic made the semifinals of the tournament for the first time by defeating Robin Soderling 6-4, 1-6, 6-3.
"(Nadal) is a big champion and plays really well on all surfaces. He is a big fighter," Djokovic said.
Nadal had two three-set wins en route to the quarters. But the Spaniard played with authority on the decisive points against Tsonga, who made 37 unforced errors.
"I started the tournament playing almost terrible and now I'm in the semifinals," Nadal said. "Today I was really focused all the time, and I played really well at the important moments."
Nadal struggled on his serve early in the first set, but managed to save five break points -- including holding for 3-3 after being down 0-40.
He gradually found his rhythm and pressured Tsonga with strong returns before breaking the Frenchman with a passing shot to lead 6-5. Nadal clinched the set with a forehand winner.
The Spaniard broke for a 6-5 lead in the second set when Tsonga missed two consecutive backhands.
"This match is exactly like my whole year," Tsonga said. "I have all the shots. I have the opportunity ... for finishing the point. And I don't finish it."
Although Nadal leads Djokovic 14-5 overall, the Spaniard was impressed by the Serb's victory over top-ranked Roger Federer in the Swiss Indoors final last week.
"He is the best player in this part of the season," Nadal said. "It's going to be a good test. I know he is the favorite on this kind of surface."
Soderling fell out of contention for the ATP finals with his loss, giving Fernando Verdasco the last available spot at the season-ending event.
Monfils entertained his home crowd with 13 aces and winners from all parts of the court on his way to his victory over Cilic.
"I don't feel tired," said 15th-seeded Monfils, who captured his second ATP title in late September in Metz. "Maybe I can dream about another title."