Porto do Itaqui, Commercial port in São Luís, Brazil.

Porto do Itaqui is a commercial port in São Luís with approximately 1,600 meters of wharf space and six berths where water depths range from 9.5 to 19 meters. The facility offers around 42,000 square meters of storage space with specialized areas for different cargo types, including grain silos.

Plans for a port at Itaqui date to 1918, when the Maranhão government granted a concession to the English firm C.H. Walker & Co. Limited, which failed. In 1939 the National Department of Ports, Rivers and Channels identified the site as suitable, but construction only began in 1966 under Serveng-Civilsan. The first 367-metre quay was completed in 1972, and operations started on 4 July 1974 under Companhia Docas do Maranhão (Codomar).

The port's name is often confused with Itaqui, a city in Rio Grande do Sul near the Argentine border, though the port lies in São Luís, Maranhão. Its hinterland covers Maranhão, Piauí, Tocantins, southwestern Pará, northern Goiás, northeastern Mato Grosso and western Bahia, and the MATOPIBA agricultural frontier accounts for 54% of exports shipped through it.

The port lies inside the Baía de São Marcos, reached by the BR-135 and BR-222 highways and by rail; the access channel is about 500 m wide and 101 km long. It is a working cargo terminal, so visits are limited to what can be seen from outside the operational area. The tide range here exceeds seven metres, among the largest in Brazil.

The access channel has a natural minimum depth of 23 metres, is about 500 metres wide and runs 101 km from the open sea to the harbour basin inside Baía de São Marcos. The basin itself holds roughly 23 metres over the reference level of the DHN.