The barangay (/bɑːrɑːŋˈɡaɪ/; abbreviated as Brgy. or Bgy.), historically known as the barrio, is the smallest administrative division in the Philippines. Named after the precolonial polities of the same name, modern barangays are political subdivisions of cities and municipalities, and are analogous to villages, districts, neighborhoods, suburbs, or boroughs. The term barangay is derived from balangay, a type of boat used by Austronesian peoples when they migrated to the Philippines.

All cities, including independent cities, and municipalities in the Philippines are politically subdivided into barangays, with the exception of the municipalities of Adams in Ilocos Norte and Kalayaan in Palawan, each of which contains only one barangay. Barangays are sometimes informally subdivided into smaller areas called purok (English: "zone"), or barangay zones consisting of clusters of houses for organizational purposes, and sitios, which are territorial enclaves—usually rural—located far from the poblacion. As of January 2025^[update], there are 42,011 barangays throughout the country.

When the first Spaniards arrived in the Philippines in the 16th century, they found well-organized, independent villages called barangays. The name barangay, also spelled balangay, originally referred to a certain type of traditional boat in many languages in the Philippines. Early Spanish dictionaries of Philippine languages make it clear that the precolonial balangay or barangay was pronounced "ba-la-ngay" or "ba-ra-ngay", while today the modern barangay is pronounced "ba-rang-gay", leading to the non-standard spelling baranggay. The pre-colonial term also referred to the people serving under a particular chief rather than to the modern meaning of an area of land, for which other words were used. While barangay is a Tagalog word, it spread throughout the Philippines as Spanish rule concentrated power in Manila.

All citations regarding pre-colonial barangays lead to a single source, Juan de Plascencia's 1589 report Las costumbres de los indios Tagalos de Filipinas. However, historian Damon Woods challenges the concept of a barangay as an indigenous political organization primarily due to a lack of linguistic evidence. Based on indigenous language documents, Tagalogs did not use the word barangay to describe themselves or their communities. Instead, barangay is argued to be a Spanish invention resulting from an attempt by the Spaniards to reconstruct pre-conquest Tagalog society.

The first barangays started as relatively small communities of around 50 to 100 families. By the time of contact with the Spaniards, many barangays had developed into large communities. The encomienda of 1604 shows that many affluent and powerful coastal barangays in Sulu, Butuan, Panay, Leyte, Cebu, Pampanga, Pangasinan, Pasig, Laguna, and the Cagayan River were flourishing trading centers. Some of these barangays had large populations. In Panay, some barangays had 20,000 inhabitants; in Leyte (Baybay), 15,000 inhabitants; in Cebu, 3,500 residents; in Vitis (Pampanga), 7,000 inhabitants; and in Pangasinan, 4,000 residents. There were smaller barangays with fewer people, but these were generally inland communities, or if they were coastal, they were not located in areas that were good for business pursuits. These smaller barangays had around thirty to one hundred houses only, and the population varied from 100 to 500 persons. According to Miguel López de Legazpi, he founded communities with only 20 to 30 people.

Traditionally, the original "barangays" were coastal settlements formed by the migration of these Malayo-Polynesian people (who came to the archipelago) from other places in Southeast Asia (see chiefdom). Most of the ancient barangays were coastal or riverine. This is because most of the people were relying on fishing for their supply of protein and their livelihood. They also traveled mostly by water, up and down rivers and along the coasts. Trails always followed river systems, which were also a major source of water for bathing, washing, and drinking.

The coastal barangays were more accessible to trade with foreigners. These were ideal places for economic activity to develop. Business with traders from other countries also meant contact with other cultures and civilizations, such as those of Japan, Han Chinese, Indians, and Arabs. These coastal communities acquired more cosmopolitan cultures with developed social structures (sovereign principalities), ruled by established royalties and nobilities.

During Spanish rule, through a resettlement policy called reductions, smaller, scattered barangays were consolidated (and thus "reduced") to form compact towns. Each barangay was headed by the cabeza de barangay (barangay chief), who formed part of the principalía, the elite ruling class of the municipalities of the Spanish Philippines. This position was inherited from the first datus and came to be known as such during the Spanish regime. The Spanish monarch, who also collected taxes (called tribute) from the residents for the Spanish Crown, ruled each barangay through the cabeza.