| Jurisdiction: | Diocese |
| Frederico Westphalen | |
| Latin: | Dioecesis Vestphaleniana |
| Country: |  Brazil |
| Province: | Passo Fundo |
| Rite: | Latin Rite |
| Established: | 22 May 1961 (years ago) |
| Cathedral: | Cathedral of Saint Anthony |
| Area Km2: | 11473 |
| Population: | 389,749 |
| Population As Of: | 2004 |
| Catholics: | 286,494 |
| Catholics Percent: | 73.5 |
| Bishop: | Antônio Carlos Rossi Keller |
| Map: | File:Diocese de Frederico Westphalen.svg |
| Website: | www.diocesefw.com.br |
The Roman Catholic Diocese of Frederico Westphalen (Latin: Dioecesis Vestphaleniana) is a diocese located in the city of Frederico Westphalen in the ecclesiastical province of Passo Fundo in Brazil.