| Jurisdiction: | Diocese |
| Gualeguaychú | |
| Latin: | Dioecesis Gualeguaychensis |
| Local: | Diócesis de Gualeguaychú |
| Country: |  Argentina |
| Metropolitan: | Paraná |
| Province: | Paraná |
| Area Km2: | 33,887 |
| Population: | 326,500 |
| Population As Of: | 2006 |
| Catholics: | 294,000 |
| Catholics Percent: | 90 |
| Parishes: | 34 |
| Denomination: | Catholic |
| Rite: | Roman Rite |
| Established: | 11 February 1957 |
| Cathedral: | St. Joseph's Cathedral, Gualeguaychú |
| Bishop: | Jorge Eduardo Lozano |
| Bishop Title: | Bishop |
| Metro Archbishop: | Juan Alberto Puiggari |
| Website: | Website of the Diocese |
The Roman Catholic Diocese of Gualeguaychú is a Latin suffragan bishopric in the ecclesiastical province of the Metropolitan Archdiocese of Paraná in Entre Ríos Province, eastern-central Argentina.
Its cathedral episcopal see is Catedral San José, dedicated to Saint Joseph, in Gualeguaychú, also in Entre Rios province, which also has a Minor basilica : Basílica de la Inmaculada Concepción del Uruguay, dedicated to the Immaculate Conception, in Concepción del Uruguay.
Established on 11 February 1957 as Diocese of Gualeguaychú / Gualeguaychen(sis) (Latin), on territory split off from its Metropolitan, the Archdiocese of Paraná.
As per 2014, it pastorally served 308,410 Catholics (89.7% of 343,789 total) on 33,887 km² in 35 parishes and a mission with 61 priests (48 diocesan, 13 religious), 4 deacons, 77 lay religious (23 brothers, 54 sisters) and 10 seminarians.