Juan José Castelli (usually abbreviated to Castelli) is a town in the province of Chaco, Argentina. It is located 274 km from the provincial capital Resistencia and has about 37,000 inhabitants as per the 2001 census [INDEC]. It is the head town of the General Güemes Department. Its population is mainly of Volga German descent. On 17 June 1936 the settlement was linked to Presidencia Roque Sáenz Peña by a railroad. This major achievement sparked the foundation of the town as such, locally acknowledged on 3 October (though the official date was that of the National Decree of 2 February 1938).