1866 in Argentina
# 1866 in Argentina

Events in the year 1866 in Argentina.

## Incumbents

* President: Bartolomé Mitre
* Vice President: Marcos Paz

### Governors

* Buenos Aires Province: Mariano Saavedra (until 1 May), Adolfo Alsina (starting 1 May)
* Mendoza Province:
   * until 1 November: Carlos González
   * 1 November-11 November: Melitón Arroyo
   * starting 11 November: Carlos Juan Rodríguez
* Santa Fe Province: Nicasio Oroño

### Vice Governors

* Buenos Aires Province: vacant

## Events

* January 31 – Paraguayan War: The Battle of Pehuajó takes place when about 1500 Paraguayan troops, commanded by General Francisco Isidoro Resquín and Lieutenant Celestino Prieto, engage in a surprise attack Argentinian and Uruguayan battalions with around 2000 men, led by General Emilio Conesa; the Paraguayans are successful and the joint Argentine-Uruguayan force suffers heavy casualties.
* May 24 – Paraguayan War: First Battle of Tuyutí is an allied victory.
* July 18 – Battle of Boquerón (1866)
* September 1–3 – Battle of Curuzú
* September 22 – Battle of Curupayty

## Deaths

* February 15 – Juan Gregorio de las Heras, military leader (born 1780)
