The canton of Saint-Malo-Sud is a former canton of France, located in the arrondissement of Saint-Malo, in the Ille-et-Vilaine département, Brittany région. It had 23,198 inhabitants (2012). It was disbanded following the French canton reorganisation which came into effect in March 2015.
The canton comprised the following communes:
At the 2011 cantonal elections, UMP councillor Gilles Lurton was elected to represent the canton of Saint-Malo-Sud in the general council of Ille-et-Vilaine department.