| Jurisdiction: | Diocese |
| San Justo | |
| Latin: | Dioecesis Sancti Iusti |
| Local: | Diócesis de San Justo |
| Country: | Argentina |
| Metropolitan: | Buenos Aires |
| Province: | Buenos Aires |
| Area Km2: | 130 |
| Population: | 1,083,000 |
| Population As Of: | 2010 |
| Catholics: | 975,000 |
| Catholics Percent: | 90 |
| Parishes: | 40 |
| Denomination: | Roman Catholic |
| Rite: | Roman Rite |
| Established: | 18 July 1969 (years ago) |
| Cathedral: | Cathedral St Justus and St Pastor in San Justo |
| Bishop Title: | Bishop |
| Bishop: | Baldomero Carlos Martini |
| Metro Archbishop: | Mario Aurelio Poli |
| Website: | Website of the Diocese |
The Roman Catholic Diocese of San Justo is located in the city of San Justo, in the province of Buenos Aires. It was established by Pope Paul VI on 18 July 1969.