Seixal () is a Portuguese city and municipality, located in the district of Setúbal, in the metropolitan area of Lisbon. Its population includes 184,269 inhabitants (2011), in an area of that includes six parishes. It is situated across the Tagus River estuary from Lisbon. Its seat is the city of Seixal, a centre of 31,600 inhabitants situated along the Rio Judeu.
The current mayor is Paulo Silva.
History
thumb|235px|left|Ecomuseu of Seixal, constructed from a river mill constructed during the 18th century
thumb|235px|left|Interior of a former cork factory in Seixal
The toponymy Seixal comes from a type of smooth stone (seixo) that is found in rivers; the name evolving from the name used to describe the geomorphology of the region.
Since the Roman era, the Tagus bay has been a region of human settlement, from many of the archaeological discoveries at Quinta do Rouxinol, in Corroios, and Quinta de S. João, in Arrentela (beginning in the period of the Portuguese Age of Discovery). A land of fishermen and signeurial holdings, the municipality of Seixal evolved over the centuries, always with the connection to the river.
Seixal is one of the eight municipalities with the most inhabitants in Portugal, and is composed of four parishes occupying a territory of :
- Amora
- Corroios
- Fernão Ferro
- Seixal, Arrentela e Aldeia de Paio Pires
Although the municipal population continued to grow with development, after the 1970s there was a boom in the population, due to improvements in accessibility and mobility, principally due to public transport, its location to Lisbon and installation of economic activities within the territory.