Since pre-history, Olhão has had vestiges of human occupation, although the oldest written record dates only from 1378, referring to a place called Olham.

[3] The estuary and abundance of water were decisive factors that influenced fishermen, at the beginning of the 17th century, to congregate along the beach of Olhão.

[3] Yet, after the middle of the 17th century, growth was driven by the protection offered by the Fort of São Lourenço do Bugio, which guarded the coast and entrance to the estuary, discouraging attacks from corsairs[who?].

[3] Over time the small town of fishermen grew into an economic, social and urban centre, resulting in its elevation in city in 1985.

[4] These deposits came to rest over sand-stones and marls that comprise the coastal Mesocenozoic, a young relief, that is little accented, aided by a platform that includes superficial lavas.

[4] The Nature Park of Ria Formosa was instituted in 1987, by Decree Law 373/87 (9 September), with the objective of protecting and conserving this river system, and in particular the flora and fauna, including species of migratory bird and their habitats.

[4] The Nature Park extends into the municipalities of Loulé, Faro, Olhão, Tavira and Vila Real de Santo António, covering an area of 18400 hectares, for 60 kilometres (37 mi) along the coast, from Ancão until Manta Rota, covering a great variety of habitats: barrier islands, marshes, banks of mud and sand, dunes, salt marshes, freshwater ponds and brackish waterways, forests and agricultural areas.

[6] Olhão is home to Sporting Clube Olhanense whose main football team plays in the Estadio José Arcanjo, a multi-purpose stadium in the city that holds 11,622 spectators and was built in 1984.