Itaguaí (Portuguese pronunciation: [itaɡwaˈi]) is a municipality located in the Brazilian state of Rio de Janeiro. Its population was 93,662 (2005) and its area is 272 km². The city was founded in 1688.
The port of Itaguaí was opened in 1982. One of its main trading goods is alumina.
The city is one of the poorest areas of the Rio de Janeiro metropolitan region. It serves also as dormitory town for workers of the industrial western zone (Zona Oeste) of Rio de Janeiro. It is the seat of the Roman Catholic Diocese of Itaguaí.