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.

Guerrero is a state in Southwest Mexico that is divided into 85 municipalities. According to the 2020 Mexican census, Guerrero is the 13th most populous state with 3,540,685 inhabitants and the 14th largest by land area spanning 63,803.42 square kilometres (24,634.64 sq mi).