Semur-en-Auxois is a commune of the Côte-d'Or department in eastern France. The engineer Edmé Régnier L'Aîné (1751–1825) and the Encyclopédiste Philippe Guéneau de Montbeillard (1720–1785) were born in Semur-en-Auxois. Semur-en-Auxois has a medieval core, built on a pink granite bluff more than half-encircled by the River Armançon. The river formerly provided motive power for tanneries and mills, but its flow is now somewhat reduced by the Lac de Pont, a dam built upstream in the 19th century to provide water for the Canal de Bourgogne.