Municipalities are the second-level administrative divisions of Mexico, where the first-level administrative division is the state. They should not be confused with cities or towns that may share the same name as they are distinct entities and do not share geographical boundaries. As of March 2024, there are 2,476 municipalities in Mexico, excluding the 16 boroughs of Mexico City.

San Nicolás is a municipality in the Mexican state of Guerrero. It is located 165 kilometres (103 mi) southeast of the state capital of Chilpancingo. It is named after its patron saint, Nicholas of Tolentino. Its creation from the municipality of Cuajinicuilapa was approved in 2021 and went into force on 21 May 2022.