Events in the year 1878 in Argentina.

• President: Nicolás Avellaneda
• Vice President: Mariano Acosta

• Buenos Aires Province: Carlos Casares (until 1 May); Carlos Tejedor (from 1 May)
• Cordoba: Antonio Del Viso
• Mendoza Province: Julio Gutiérrez (until 15 February); Elías Villanueva (from 15 February)
• Santa Fe Province: Servando Bayo then Simón de Iriondo

• Buenos Aires Province: Luis Sáenz Peña (until 1 May); José María Moreno (starting 1 May)

• May 23 - chartering of Bank of the City of Buenos Aires as the Monte de Piedad in a measure against the prevalence of usury in Buenos Aires (mostly targeting the growing wave of immigration in Argentina)^[1]

• January 8 – Gauchito Gil, legendary religious figure (b. 1847)