Municipalities of Puerto Rico in the context of "Castillo San Felipe del Morro"

The barrios of Puerto Rico are the third-level administrative divisions defined with geographic boundaries serving as the primary legal subdivisions of the 78 municipalities in the archipelago and island of Puerto Rico, an unincorporated territory of the U.S. Amounting to 902 wards or boroughs equivalent to minor civil divisions in the U.S., like cities, townships, and parishes, barrios are under the governmental authority of the popularly elected strong mayor and unicameral legislature governing the municipality within which they are located. Barrios are subdivided into numerous subbarrios, districts, communities, and/or sectors.

Except for San Juan, Ponce, Florida, and Vieques, all municipalities have a barrio equivalent to a downtown area in the U.S. called pueblo, officially known as barrio-pueblo (literally "neighborhood-town"), which typically is the site of the historic Spanish colonial settlement, administrative center, and urban core of the municipality. Of the 902 barrios proper, 828 are barrios and 74 barrios-pueblos.

Puerto Rico (abbreviated PR), officially the Commonwealth of Puerto Rico, is a self-governing Caribbean archipelago and island organized as an unincorporated territory of the United States under the designation of commonwealth. Located about 1,000 miles (1,600 km) southeast of Miami, Florida, between the Dominican Republic in the Greater Antilles and the U.S. Virgin Islands in the Lesser Antilles, it consists of the eponymous main island and numerous smaller islands, including Vieques, Culebra, and Mona. With approximately 3.2 million residents, it is divided into 78 municipalities, of which the most populous is the capital municipality of San Juan, followed by those within the San Juan metropolitan area. Spanish and English are the official languages of the government, though Spanish predominates.

Puerto Rico was settled by a succession of Amerindian peoples beginning 2,000 to 4,000 years ago; these included the Ortoiroid, Saladoid, and Taíno. It was claimed by Spain following the arrival of Christopher Columbus in 1493 and subsequently colonized by Juan Ponce de León in 1508. Puerto Rico was contested by other European powers into the 18th century but remained a Spanish possession for the next 400 years. The decline of the Indigenous population, followed by an influx of Spanish settlers, primarily from the Canary Islands and Andalusia, and African slaves vastly changed the cultural and demographic landscape of the archipelago. Within the Spanish Empire, Puerto Rico played a secondary but strategically significant role compared to larger and wealthier colonies like Peru and New Spain. By the late 19th century, a distinct Puerto Rican identity began to emerge, centered on a fusion of European, African, and Indigenous elements. In 1898, following the Spanish–American War, Puerto Rico was acquired by the United States.

San Juan (/ˌsæn ˈhwɑːn/ san WHAHN, Spanish: [saŋ ˈxwan]; Spanish for "Saint John") is the capital city and most populous municipality in the Commonwealth of Puerto Rico, an unincorporated territory of the United States. As of the 2020 census, it is the 57th-most populous city under the jurisdiction of the United States, with a population of 342,259. San Juan was founded by Spanish colonists in 1521, who called it Ciudad de Puerto Rico (Spanish for "Rich Port City").

Puerto Rico's capital is the second oldest European-established capital city in the Americas, after Santo Domingo, in the Dominican Republic, founded in 1496, and is the oldest European-established city under United States sovereignty. Several historical buildings are located in the historic district of Old San Juan; among the most notable are the city's former defensive walls, Fort San Felipe del Morro and Fort San Cristóbal, and La Fortaleza, the oldest executive mansion in continuous use in the Americas. These historic sites were declared a UNESCO World Heritage Site in 1983.

Ponce (US: /ˈpɔːnseɪ, ˈpoʊn-/ PAWN-say, POHN-, UK: /ˈpɒn-/ PON-, Spanish: [ˈponse] ) is a city and a municipality on the southern coast of Puerto Rico. The most populated city outside the San Juan metropolitan area, Ponce was founded on August 12, 1692 and is named after Juan Ponce de León y Loayza, the great-grandson of Spanish conquistador Juan Ponce de León. Ponce is often referred to as La Perla del Sur (The Pearl of the South), La Ciudad Señorial (The Manorial City), and La Ciudad de las Quenepas (Genip City).

The city serves as the governmental seat of the autonomous municipality as well as the regional hub for various government of Puerto Rico entities, such as the Supreme Court of Puerto Rico. It is also the regional center for various U.S. federal government agencies. Ponce is a principal city of both the Ponce Metropolitan Statistical Area and the Ponce-Yauco-Coamo Combined Statistical Area with, as of the 2020 US Census, a population of 278,477 and 333,426 respectively.

Florida (Spanish pronunciation: [floˈɾiða]) is a town and municipality of Puerto Rico located in the karst region north of Ciales, south of Barceloneta, east of Arecibo, and west of Manatí. Florida is not like other municipalities of Puerto Rico with multiple subdivisions called barrios. It has one barrio called Florida Adentro and two other subdivisions: Florida Zona Urbana and Pajonal comunidad. It is part of the San Juan-Caguas-Guaynabo Metropolitan Statistical Area.

Vieques (/viˈeɪkəs/ ; Spanish pronunciation: [ˈbjekes], locally [ˈbjekeʔ]), officially the Isla de Vieques, is an island and municipality of Puerto Rico, comprising the Spanish Virgin Islands together with Culebra.   Located about 8 miles (13 km) east of the main island of Puerto Rico, it is about 20 miles (32 km) long and 4.5 miles (7 km) wide. Vieques is spread over 7 barrios and Isabela Segunda (or "Isabel the Second", sometimes written "Isabel II"), its historic and administrative center. Residents of the island are known as viequenses. The population of the island is 8,249 as of the 2020 Census.

The island's name is a Spanish spelling of a Taíno word said to mean "small island" or "small land". It also has the nickname Isla Nena, usually translated as "girl island" or "little girl island", alluding to its perception as Puerto Rico's little sister. The island was given this name by the Puerto Rican poet Luís Lloréns Torres. During the British colonial period, its name was Crab Island.

The government of Puerto Rico encompasses the local administrative structure of the archipelago and island of Puerto Rico, an unincorporated territory of the U.S. organized under the Constitution of Puerto Rico since its establishment as the Commonwealth of Puerto Rico in 1952. The government is a republican democracy divided into three branches: the law-implementing executive, the law-making legislative, and the law-interpreting judicial. The Governor is the chief executive, the Legislative Assembly is the legislature, and the Supreme Court is the highest court of the territory, which is divided into 78 municipalities, each one headed by a strong mayor and a unicameral legislature. Like U.S. states and other U.S. territories, Puerto Rico is subject to the sovereign jurisdiction of the U.S. federal government.

With the American annexation of Puerto Rico during the Spanish–American War, the U.S. established a military government to administer the unincorporated territory from 1898 to 1900, when it was replaced by a civil insular government organized under the organic acts of the Foraker Act from 1900 to 1917 and the Jones–Shafroth Act from 1917 to 1952. The Constitution of Puerto Rico established the Commonwealth of Puerto Rico and its government under the continued status of unincorporated territory in 1952. With the ratification of the constitution, the full authority and responsibility for the local administration of Puerto Rico was vested in the residents of Puerto Rico, resulting in complete self-governance within the archipelago and island.

Culebra, officially Isla de Culebra (Spanish pronunciation: [kuˈleβɾa], "Snake Island"), is an island and municipality of Puerto Rico, comprising the Spanish Virgin Islands together with Vieques. Located about 17 miles (27 km) east of the main island of Puerto Rico, it is 9 miles (14 km) northeast of Vieques and 12 miles (19 km) west of Saint Thomas in the U.S. Virgin Islands. Culebra is spread over 5 barrios and Culebra Pueblo, its historic and administrative center. Residents of the island are known as culebrenses. With a population of 1,792 as of the 2020 Census, it is the least populous municipality in Puerto Rico.

Originally called Isla del Pasaje and Isla de San Ildefonso, Culebra is also known as Isla Chiquita ("Little Island"), Cuna del Sol Borincano ("Cradle of the Puerto Rican Sun") and Última Virgen ("Last Virgin", due to its position at the end of the Virgin Islands archipelago).

The San Juan–Bayamón–Caguas metropolitan area, most commonly known as the San Juan metropolitan area (Spanish: área metropolitana de San Juan), is the largest and most populous metropolitan statistical area (MSA) in Puerto Rico, concentrated in the capital municipality of San Juan and surrounding municipalities, including Bayamón, Caguas, and Carolina, on the northeastern coastal plain of the main island. One of 6 metropolitan statistical areas in Puerto Rico, it is within the San Juan–Bayamón combined statistical area (CSA), which is one of 3 primary statistical areas in the archipelago as defined by the United States Census Bureau. As of 2023, the estimated population of the San Juan–Bayamón–Caguas metropolitan area is 842,535 in municipalities in the conurbation and 1,193,198 in municipalities outside the urban core, making it the fourth largest in the insular Caribbean.