1866 in Argentina
Events in the year 1866 in Argentina.
Incumbents
Governors
- Buenos Aires Province: Mariano Saavedra, Adolfo Alsina
- 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