Guinea-Bissau's capital and largest city is Bissau. It had a population of 492,004 as of the year 2015. Bissau is Guinea-Bissau's largest city, major port, and administrative and military hub, and it is off the Atlantic Ocean in the Geba River estuary.
Portugal established the city in 1687 as a fortified port and trading hub. In 1942, Bissau replaced Bolama as the capital of Portuguese Guinea.

When the anti-colonial guerrillas of PAIGC declared independence in 1973, Madina do Boe became the rebel territories' capital, while Bissau remained the colonial capital. Following the military coup in Lisbon on April 25, Bissau became the new independent state's capital when Portugal granted independence.

During the beginning and end of the Guinea-Bissau Civil War in 1998 and 1999, Bissau was the scene of intense fighting.