Goals from Kylian Mbappe and Vitinha ensured a seventh consecutive league win for Luis Enrique's team. PSG has a four-point cushion at the top after second-place Nice was handed its first loss this season on Saturday, a 1-0 defeat at Nantes.
Le Havre got off to a strong start with several good moves but lacked accuracy to inflict any damage. The hosts produced 22 shots, but only seven of them were on target.
Donnarumma was sent off following a reckless foul outside his box. The Italy goalkeeper came out of the area as he tried to clear a long ball with a very high tackle, but instead made contact with Le Havre forward Josue Casimir's face.
Referee Bastien Dechepy showed him a red card and Bradley Barcola made way for substitute goalie Arnau Tenas.
PSG broke the deadlock on the break after Lee Kang-in set up Ousmane Dembele down the right side. The winger then crossed the ball for Mbappe, who controlled with his right foot and curled a shot into the net from the edge of the box in the 22nd minute. It was Mbappe's 15th league goal this season.
Vitinha completed PSG's win in the 88th minute from Manuel Ugarte's assist.
Also Sunday, the French league (LFP) mourned the death of a Nantes supporter who was killed before the match between Nantes and Nice on Saturday in the latest incident to mar French soccer this season.
“The LFP would like to express its most sincere condolences to the victim's family and friends, and to the FC Nantes club,” the league said.