According to Goldbeck, the town Braunsberg has been named after Bruno von Schauenburg (c. 1205–1281), Bishop of Olomouc (1245–1281), who had accompanied king Ottokar II of Bohemia in 1254 and 1267, when the king participated in the crusade of the Teutonic Knights in Prussia. Bruno von Schauenburg is also known as the founder of the village of Brušperk in Bohemia, the German name of which is Braunsberg too. It has also been suggested that the name Brausnberg might have been deduced from the name of the settlement Brusebergue (`camp of the prussians´). Reliable historical documents on the town are available since 1278.
In 1243 the settlement, together with the surrounding region of Warmia, was given by the Order to the newly created Bishopric of Warmia, whose bishop built his cathedral in the town and made it his chief residence. Braunsberg was granted town privileges based on those of Lübeck in 1254, but was destroyed and depopulated in the second uprising of native Prussians in 1261. It was rebuilt in a new location in 1273 and settled by newcomers from Lübeck. In 1284 Braunsberg was given a new town charter, again based on the laws of Lübeck. However, the next bishop, Heinrich Fleming (1278–1300) transferred the chapter from Braunsberg to Frauenburg (Frombork) where it remained until the 20th century.
In 1296 a Franciscan abbey was built in Braunsberg, and in 1342 a "new town" (still called Neustadt or Nowe Miasto) was added. Braunsberg became a prosperous member of the Hanseatic League. The town remained a part of the monastic state of the Teutonic Knights until 1466, when as a consequence of the Second Peace of Thorn ending the Thirteen Years' War, it passed to the Kingdom of Poland as part of the new autonomous province of Royal Prussia. In 1487 it withstood a siege by Polish troops during the War of the Priests.
During the reign of Duke Albert in the neighboring Duchy of Prussia, a large part of Braunsberg's populace converted to Lutheran Protestantism. Albert sought to unite Warmia with Ducal Prussia, causing the Catholics of the town to swear allegiance to the king of Poland in return for aid against Protestant Prussia. In 1526 a Polish royal commission released Braunsberg's burghers from the oath to the Polish king and handed the town back to Prince-Bishop Mauritius Ferber. Braunsberg swore allegiance to the Prince-Bishops of Warmia, but had to denounce all Lutheran teachings and hand over Lutheran writings.
The town suffered from warfare and the church tower was not rebuilt until 1544, when Prince-Bishop Johannes Dantiscus ordered 20 zentners' weight of copper from Anton Fugger in Augsburg. It could only be paid off slowly with yearly payments of 100 marks. For many years Braunsberg was not able to directly attend Hanseatic meetings; it was not until 1557 that representatives attended session in Lübeck again.
During Prince-Bishop Stanislaus Hosius' government, Lutheran teachings again became popular in Braunsberg. They were suppressed when Hosius brought in the Jesuits and founded the Collegium Hosianum school. The Jesuit theologian Antonius Possevinus was instrumental in enlarging the Collegium Hosianum to receive Swedes. A priest seminary was added in 1564. Pope Gregory XIII later added a papal mission seminary for northern and eastern European countries. Regina Protmann, a native of Braunsberg, founded the Saint Catherine Order of Sisters in the town, recognized by the church in 1583. The Jesuit theologian Antonius Possevinus was instrumental in enlarging the Collegium Hosianum in the 1580s to educate Swedes and Ruthenians there as well in order to counter the widespread Protestant movement.
The ethnically German, politically Polish, and primarily Catholic town was annexed by the mostly Protestant Kingdom of Prussia in 1772 during the First Partition of Poland and made part of the province of East Prussia the following year. Braunsberg obtained its first railway connection in 1852. In 1871 it became part of the newly established German Empire during the Prussian-led unification of Germany.
During World War II, Braunsberg was occupied by the Soviet Red Army following the Braunsberg Offensive Operation (13 March 1945 - 22 March 1945) following the elimination of the German Heiligenbeil Pocket, and suffered heavy destruction due to fighting and subsequent looting. The German inhabitants of the town were either evacuated before the Red Army arrived, killed during the fighting, or expelled westward after the war by the Poles. It was placed under administration of the People's Republic of Poland according to the Potsdam Conference in 1945. The town of Braunberg was then renamed to Braniewo by Polish authorities..
In 2001 the St. Catherine Church, built in 1346, destroyed in 1945, and rebuilt after 1979, was declared a Basilica Minor (Bazylika Mniejsza). This Gothic Hall church was built on a site, which held a previous wooden Church of St. Catherine since 1280. Prince-Bishop Lucas Watzenrode of Warmia had added extensively to the building.
Number of inhabitants by year