Angra do Heroísmo, officially the Very Noble, Loyal and Ever Steadfast City of Angra do Heroísmo, or simply Angra, is a city and municipality on Terceira Island, Portugal, and one of the three capital cities of the Azores. Founded in 1478, Angra was historically the most important city in the Azores, as seat of the Bishop of the Azores, government entities, and having previously served as the capital city of Portugal during the Liberal Wars. The population in 2011 was 35,402, in an area of 239.00 km². It was classified as a World Heritage site by UNESCO in 1983.

Angra is the Portuguese word for "inlet", "cove", or "bay". The epithet do Heroísmo ("of Heroism", "the Heroic") was granted to the city by Maria II to commemorate its citizens' successful defense of the island against a Miguelist assault in 1829. The full name of the city is the Very Noble, Loyal and Ever Steadfast City of Angra do Heroísmo (Portuguese: Muito nobre, leal e sempre constante cidade de Angra do Heroísmo).

Some claim that Angra was founded by Álvaro Martins, who sailed with Didrik Pining on his expedition to the New World, and with Bartolomeu Dias on his voyage around the Cape of Good Hope. Others contend that Angra was founded in 1450 or 1451 by Jácome de Bruges, a Fleming in the service of Prince Henry the Navigator, who recruited farmers, fishermen, and merchants in the Low Countries to colonize the Azores.

The first references to the settlement of the Azores date to between 1439 and 1449, through the donation of Henry the Navigator the colonization of seven islands in the central and eastern groups of the archipelago. Terceira, included in this group, would be administered by Jácome de Bruges as stipulated in the nomination process, dated March 1450, that included not only the settlement of the lands, but also the milling monopoly, ovens, salt concession, land rights in the name of the monarchy, tithes, administration of justice, and rights of succession including the exceptional provision for materlineal succession. But, the great difficulty in attracting settlers meant that by 22 August 1460, the island was still unpopulated.

The site chosen by the first settlers was a ridgeline, which opened, like an amphitheatre, onto two small bays, separated by a peninsula, at the head of which stood the extinct volcano of Monte Brasil. One of these coves was deep enough (around 40 m or 130 ft) to provide an anchorage for large vessels, and it had the further advantage of being sheltered from most strong winds, except for those from the south and southeast.

In 1474, Álvaro Martins Homem ordered that the river flowing into the cove be diverted into a manmade stone-lined channel, running downhill, so that its rushing waters could be harnessed to turn the waterwheel of a mill. This laid the foundation for the future economic development of the village of Angra. At the same time, this allowed the area on either side of the river's course to be rearranged according to a rectilinear street-plan and organized into neighborhoods by function (commercial, residential, etc.), to accommodate the needs of the fast-growing port. The first houses of Angra were built on the hillside above the cove, the steep streets winding down to the shore. On high ground, away from the sea, a castle/stronghold/fortress was begun; it would eventually be named Castelo dos Moinhos (English: Castle of the Mills). By 1534, Angra was the first town in the archipelago to be elevated to the status of city. In the same year, it was chosen by Pope Paul III to be the seat of the Diocese of Angra, with ecclesiastical authority over all of the islands of the Azores.

The commercial port of early Angra played an important role in the Portuguese East Indies trade beginning in the 15th century. The bay of Angra was often full of caravels and galleons, a circumstance that contributed to the progress of the city and its people. The construction of a number of manors, convents, churches, and military fortifications in Angra, infrastructures that were usually inappropriate for a small city (or small island) indicates the important role that Angra played in trans-Atlantic shipping for the Portuguese. The Portuguese nobleman Pero Anes do Canto (1480–1556), who was born at Guimarães, was the superintendent of fortifications on Terceira. For his competency in that role, and other services to the Portuguese Crown, he was rewarded with the title moço fidalgo (knight-gentleman), and the high office of "Purveyor to the Armada of the Islands and the merchant vessels of the East India trade in all of the islands of the Azores" (a hereditary title that followed successive members of the Canto family for three hundred years). The importance and power of the Cantos can hardly be overstated. During the period when Portugal was trading with its Asian, African, and South American colonies, they were responsible for the protection and welfare of the merchant fleet (and the staggering wealth represented by the cargoes in their holds) once the ships approached the last leg of their voyages in the North Atlantic. They were also responsible for acting as the chief customs official, the chief magistrate charged with resolving disputes, and the overseer of the naval defenses of the Azores.

Before Philip II of Spain had a chance to enforce his claim to the crown of Portugal, in 1580, António, Prior of Crato, an illegitimate scion of the Beja line of the House of Braganza Portuguese royal family, proclaimed himself king on 24 July 1580. However, his rule in continental Portugal lasted only twenty days; on 25 August, he was defeated at the Battle of Alcântara by the Spanish Habsburg armies led by Fernando Álvarez de Toledo, Duke of Alba.