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.

This article on a Roman Catholic diocese in Argentina is a stub.