The origins of Bangor date back to the founding of a monastic establishment on the site of Bangor Cathedral by the Celtic saint Deiniol in the early 6th century AD.

In 973, Iago ab Idwal, ruler of the Kingdom of Gwynedd, was usurped by Hywel, and requested help from Edgar, King of England. Edgar, with an army, went to Bangor and encouraged both Iago and Hywel to share the leadership of the realm. Asserting overall control however, Edgar confirmed liberties and endowments of the Bishop of Bangor, granting land and gifts.

Bangor remained a small settlement, but development was spurred by slate mining at nearby Bethesda, beginning in the 1770s, becoming one of the largest slate quarries in the world.

The university was founded in 1884 with 58 students and ten staff as the University College of North Wales in a former inn. Students were awarded degrees from the University of London until 1893. In 1893, Bangor was one of the three founding colleges of the University of Wales

In 1911, the university moved to the purpose-built Tudor-style building on the hill overlooking the city. The Department of Welsh Studies gained international recognition under Bedwyr Lewis Jones in the 1970s.

In the 2020/2021 academic year, 9,705 people were enrolled at Bangor University,