Marignac-Lasclares (; ) is a commune in the Haute-Garonne department in southwestern France.
The commune is bordered by four other communes: Gratens to the north, Le Fousseret to the west and southwest, Lafitte-Vigordane across the river Louge to the east, and finally by Saint-ÃÂlix-le-Château across the river Louge to the southeast.
The river Louge flows in the commune, forms a border between Lafitte-Vigordane and Saint-ÃÂlix-le-Château.