Aunay-sur-Odon (French pronunciation: [onɛ syʁ ɔdɔ̃] ⓘ, literally Aunay on Odon) is a former commune in the Calvados department in the Normandy region of north-western France.

[3] The commune is located at the foot of the foothills of the Armorican Massif on the Odon river a few kilometres east from its source.

It is at the heart of the Pre-Bocage country of transition between the Caen plain, the Bessin, and the Bocage virois with which it is also connected.

The D54 joins Cahagnes and Caumont-l'Éventé in the north-west through the village to Roucamps, Le Plessis-Grimoult, and Condé-sur-Noireau in the south.

Several small tributaries feed it such as the Douvette which marks the boundary with Courvaudon in the east and the Ruisseau du Val Boquet on the north-west border.

The highest point of 307 to 310 metres (1,007 to 1,017 ft) is located in the south on the border with Roucamps in a wood overlooking a place called Pied de la Bruyère.

The town is located that had been already occupied in the Gallo-Roman era as it was at the crossroads of ancient routes from Vieux to Avranches and from Bayeux to Condé-sur-Noireau.

The Roman de Rou by Wace mentions a Lord of Alnei[8] said to have participated in the conquest of England along with William the Conqueror.

The remains of his castle from the 12th century, overlooking the present Petit Pied du Bois, are described in the third volume of the Monumental statistic of Calvados (in French) by Arcisse de Caumont (1857).

In 1944 due to its position as a crossroads, this time between Caen and Vire and between Bayeux and Falaise, the city suffered two strategic bombardments by the Allies.