Sainte-Martine is a municipality in Beauharnois-Salaberry Regional County Municipality in the Montérégie region of Quebec, Canada. The population as of the 2021 Canadian census was 5,664. The municipality is made up of a large northern section and a small unattached southern area that was known as the municipality of Saint-Paul-de-Châteauguay until its merger with Sainte-Martine on September 9, 1999.