Brewer is a city in Penobscot County, Maine, United States. It is part of the Bangor metropolitan area. The city is named after its first settler, Colonel John Brewer. The population was 9,672 at the 2020 census. Brewer is the sister city of Bangor. The two are at the head of navigation on opposite sides of the Penobscot River estuary and are connected by three bridges.