Sao Luis is a major port city, capital and largest city in Maranhao state (Brazil) with population over 1 million (metro over 1,2 million).
- The city is located on Saint Louis Island (Ilha de Sao Luis) in Baia de Sao Marcos (bay) on the Atlantic Ocean. The town was originally named Saint-Louis-de-Maragnan, established by France as one of the 3 Brazilian state capitals built on islands (the others are Vitoria and Florianopolis).
- The city has two major seaports - Itaqui and Madeira, through which most of Brazil's iron ore is exported. City's main industry is metallurgy - represented by the Alcoa Corporation (USA) ranked world's 6th largest aluminium producer.
- Port Itaqui is currently world's 2nd deepest seaport - after Rotterdam Holland, and one of country's busiest, exporting iron ore (from Carajas Mines) and industrial products due to its proximity to strategic port cities in USA and Europe.
- In 1997, city's historical downtown was designated UNESCO Site. Road BR135 (via Estreito dos Mosquitos bridge) connects Sao Luis Island to mainland Brazil.