Below are notable events in archaeology that occurred in 1866.

Explorations Architect Thomas Drew draws attention to the significance of St. Audoen's Church, Dublin, Ireland.

Excavations Discovery and first excavation of Fertőrákos mithraeum. Amateur antiquarian John Mellor excavates at the site of Hyde Abbey near Winchester in England, finding bones which he presumes to be of Alfred the Great.

Publications Posthumous publication by Édouard Lartet of Henry Christy's Reliquiae Aquitanicae, being contributions to the archaeology and palaeontology of Perigord and the adjacent provinces of southern France commences.

Finds February 26 - The Calaveras Skull is discovered in California. Purported to be evidence of humans in North America during the Pliocene epoch, it turns out to be a hoax. The prehistoric sculpture Swimming Reindeer is found in France. The first copy of the Decree of Canopus is found at Tanis.

Births May 23 - Edgar J. Banks, American antiquarian (d. 1945). June 26 - George Herbert, 5th Earl of Carnarvon, British Egyptological excavation sponsor (d. 1923). See also List of years in archaeology 1865 in archaeology 1867 in archaeology

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