Jean-Baptiste-Gustave Lamothe (April 16, 1856 – November 24, 1922) was a Canadian judge and lawyer.
He studied the cours classique at the Séminaire Saint-Joseph de Trois-Rivières, and Law with François-Xavier-Anselme Trudel in Montreal.
He was awarded a doctorate in Law by the Université de Montréal in 1921.
Involved with the Parti conservateur du Québec, he was vice president of the Association libérale-conservatrice de Montréal.
He was appointed a judge of the Quebec Superior Court on September 25, 1915.