Saturday's result was a welcomed boost for the Principality side, who had their two previous games across all competitions.
Goals from Wilfried Singo and Breel Embolo sealed Monaco's ninth win in 14 French league matches. They have a three-point lead over third-place Marseille, who travels to Saint-Etienne on Sunday.
Monaco coach Adi Hütter kept his usual system but made some changes, with 18-year-old striker George Ilenikhana up front and Maghnes Akliouche, Takumi Minamino and Aleksandr Golovin behind him.
The coach also needed to find a last-minute replacement for captain Denis Zakaria, who was ruled out because of pain in his thigh. A first start of the season was handed to midfielder Eliot Matazo.
Monaco enjoyed most of the possession in the first half and had the best chances. Ilenikhana hit the right post and struck the crossbar.
Singo broke the deadlock five minutes into the second half from a set-piece. The Ivory Coast defender connected with Lamine Camara's free kick with a decisive header. Embolo made it 2-0 with eight minutes left from another header.
Toulouse were in 10th place, 16 points off leader PSG's pace. PSG were held 0-0 at Auxerre on Friday.
Monaco were without US striker Folarin Balogun, who last week took another hit on his recently dislocated shoulder, putting him in doubt for next week's match against his former club Arsenal.
On a successful day for the French Riviera clubs, Nice defeated struggling Le Havre 2-1 and remained six points behind local rivals Monaco.
Depleted by injuries, hosts Nice took the lead in the 55th minute. Awarded a penalty for a handball in the box, Gaetan Laborde converted it. Laborde turned provider 20 minutes later, picking Badredine Bouanani for Nice's second goal.
Gautier Lloris reduced Le Havre's deficit in added time.
Lyon won at Angers 3-0 with a brilliant attacking display and extended their unbeaten run across all competitions to eight matches.
The last defeat was on Oct. 24 against Besiktas in the Europa League.
Lyon midfielder Ryan Cherki enjoyed a superb night. Even Angers fans applauded in appreciation when he was substituted. Cherki served up the corner that led to Nicolas Tagliafico's opener then capped a brilliant collective move with a goal of his own from inside the box.
Georges Mikautadze added more luster to the win with a great goal. The Georgia forward skipped past two players on the left side then burst into the area and scored from a tight angle with a powerful strike.
Lyon moved up to fifth place, nine points behind PSG.
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