A balangay, or barangay, is a type of lashed-lug boat built by joining planks edge-to-edge using pins, dowels, and fiber lashings. They are found throughout the Philippines and were used largely as trading ships up until the colonial era. The oldest known balangay are the eleven Butuan boats, which have been carbon-dated individually from 689 to 988 CE and were recovered from several sites in Butuan, Agusan del Norte. The Butuan boats are the single largest concentration of lashed-lug boat remains of the Austronesian boatbuilding traditions. They are found in association with large amounts of trade goods from East Asia, Southeast Asia, and as far as Persia, indicating they traded as far as the Middle East.

Balangay were the first wooden watercraft excavated in Southeast Asia. Balangay are celebrated annually in the Balanghai Festival of Butuan.

Balangay was one of the first native words the Europeans learned in the Philippines. The Venetian chronicler Antonio Pigafetta, who was with Ferdinand Magellan when setting foot in the Philippines in 1521 called the native boats balangai or balanghai. This word appears as either balangay or barangay, with the same meaning, in all the major languages of the Philippines. Early colonial Spanish dictionaries make it clear that balangay and barangay were originally pronounced "ba-la-ngay" and "ba-ra-ngay", but due to centuries of Spanish influence, the modern barangay is pronounced "ba-rang-gay" in modern Filipino (/bɑːrɑːŋˈɡaɪ/, instead of precolonial /bɑːrɑːŋˈaɪ/). Pigafetta's alternate spelling with an H, balanghai, later gave rise to the historically incorrect neologism balanghay in the 1970s (with a new, slightly different pronunciation which Pigafetta did not intend).

The term was also used by the Tagalog people to refer to the smallest discrete political units, which came to be the term used for native villages under the Spanish colonial period. The name of the boat was usually Hispanicized in Spanish and American records as barangayan (plural: barangayanes) to distinguish them from the political unit.

Among the Ibanag people of Northern Luzon, balangay were known as barangay, a term sometimes extended to the crew. Large vessels were called biray or biwong.

In the Visayas and Mindanao, there are multiple names for balangay-type boats, including baloto (not to be confused with the balutu), baroto, biray, lapid, tilimbao (or tinimbao). Cargo-carrying versions of balangay with high sides and no outriggers (which necessitated the use of long oars instead of paddles) were also known as bidok, birok, or biroko (also spelled biroco) in the Visayas. The karakoa, a large Visayan warship, was also a type of balangay.

"Balangay" is a general term and thus applies to several different types of traditional boats in various ethnic groups in the Philippines. In common usage, it refers primarily to the balangay of the Visayas and Mindanao islands, which were primarily inter-island trading ships, cargo transports, and warships. Large balangay (especially warships), including the Butuan boats, are commonly equipped with large double-outriggers which support paddling and fighting platforms, in which case, they can be generically referred to as paraw or tilimbao (also tinimbao, from timbao, "outrigger"). Balangay warships, along with the larger karakoa, were regularly used for raiding (mangayaw) by Visayan warriors. It is believed that they may have been the "Pi-sho-ye" raiders described as regularly attacking Chinese settlements on the coast of Fujian in the 12th century AD.

"They (Visayans) have many kinds of ships of very different designs and names for fighting their wars and making their voyages. Most of the ones they use for wars and raiding are small; they are called barangay. And if they are a little bigger, they are called biray. The latter are very long and narrow, the smaller seating 50 and the larger ones 100, all of whom must row except the chief who is aboard the ship. The oars [sic] of these ships are a little more than a vara in length; their shafts are very well made. The oars are not fastened to the boat for rowing; instead the seated oarsmen ply gently with both hands. These vessels are extremely swift. They hold two or three banks of seated oarsmen on a side, provided there are enough people to fill them. And these banks are placed in counterweights (outriggers), which are made of a very large bamboo plant found on all the Philippine Islands of the West. These counterweights are placed on the outer sides of the vessel, where the oarsmen are seated comfortably. These vessels travel very safely with these counterweights because they cannot capsize, and the counterweights also allow them to travel in heavy seas because the ship is elevated above the level of the water, so the waves break against the counterweights and not against the boats. They have round sails like ours."