| Jurisdiction: | Diocese |
| Itaguaí | |
| Latin: | Dioecesis Itaguaiensis |
| Province: | São Sebastião do Rio de Janeiro |
| Rite: | Latin Rite |
| Established: | 14 March 1980 (years ago) |
| Cathedral: | Catedral São Francisco Xavier |
| Area Km2: | 2,549 |
| Population: | 358,000 |
| Population As Of: | 2004 |
| Catholics: | 240,000 |
| Catholics Percent: | 67.0 |
| Metro Archbishop: | Orani João Tempesta, OCist |
| Bishop: | José Ubiratan Lopes, OFMCap |
The Roman Catholic Diocese of Itaguaí (Latin: Dioecesis Itaguaiensis) is located in the ecclesiastical province of São Sebastião do Rio de Janeiro in Brazil.
14 March 1980: Established as Diocese of Itaguaí from the Diocese of Barra do Piraí–Volta Redonda and Diocese of Nova Iguaçu