| Jurisdiction: | Diocese |
| Rio do Sul | |
| Latin: | Dioecesis Rivi Australis |
| Local: | Diocese de Rio do Sul |
| Country: | Brazil |
| Metropolitan: | Florianópolis |
| Rite: | Latin Rite |
| Established: | 23 November 1968 (years ago) |
| Cathedral: | Cathedral St John the Baptist in Rio do Sul |
| Area Km2: | 9,659 |
| Population: | 308,000 |
| Population As Of: | 2010 |
| Catholics: | 253,000 |
| Catholics Percent: | 82.1 |
| Metro Archbishop: | Wilson Tadeu Jönck, SCI |
| Emeritus Bishops: | Augustinho Petry |
| Map: | File:Diocese de Rio do Sul.svg |
| Website: | Website of the Diocese |
The Roman Catholic Diocese of Rio do Sul (Latin: Dioecesis Rivi Australis) is a diocese located in the city of Rio do Sul in the ecclesiastical province of Florianópolis in Brazil.