The municipalities of Puerto Rico are the second-level administrative divisions in the Commonwealth of Puerto Rico. There are 78 such administrative divisions covering all 78 incorporated towns and cities. Each municipality is led by a mayor and divided into barrios, third-level administrative divisions, though the latter are not vested with any political authority. Every municipality is governed as stated by the Autonomous Municipalities Act of 1991, which establishes that every municipality must have an elected strong mayor with a municipal legislature as the form of government. Each legislature must be unicameral, with the number of members related to adequate representation of the total population of the municipality. In contrast to other jurisdictions, both the mayors and the municipal legislators are elected on the same date and for the same term of four years in office.

Puerto Rico, officially the Commonwealth of Puerto Rico, is a Caribbean island, Commonwealth, and unincorporated territory of the United States. It is located in the northeast Caribbean Sea, approximately 1,000 miles (1,600 km) southeast of Miami, Florida, between the Dominican Republic and the U.S. Virgin Islands, and includes the eponymous main island and several smaller islands, such as Mona, Culebra, and Vieques. With roughly 3.2 million residents, it is divided into 78 municipalities, of which the most populous is the capital municipality of San Juan. Spanish and English are the official languages of the executive branch of government, though Spanish predominates.