Gualeguay is a department of the province of Entre Ríos in the Argentine Republic. It is the largest in the province with 7178 km² and the eighth most populated, with 51 883 inhabitants according to the 2010 census. It is bordered to the west by the Victoria department, to the north by the departments of Nogoyá and Tala, to the south by the province of Buenos Aires Aires, to the southwest with the province of Santa Fe and to the east with the departments of Gualeguaychú and Islas del Ibicuy. The islands of the Lechiguanas in the delta of Paraná are part of the department.
According to the methodology used by the INDEC for the censuses of 1991,2001 and 2010, the Gualeguay department comprised 5 localities: Aldea Asunción, Lazo Station, General Galarza, Gualeguay, Puerto Ruiz.