San Pedro Lagunillas is a municipality and its corresponding municipal seat located in the Mexican state of Nayarit. It holds the distinction of being the least populous municipality within the state.
As of 2005, the municipality had a total population of 7,155 people across an area of 520 square kilometers, while the town and municipal seat specifically housed 3,630 residents. The local population has been in a steady decline since 1980, when it recorded 8,308 inhabitants.