The capital of the Unelli, a Gaulish tribe, the town was given the name of Constantia in 298 during the reign of Roman Emperor Constantius Chlorus.

The town was destroyed by the invading Normans in 866; they later established settlements and incorporated the whole peninsula into the Duchy of Normandy in 933.

On 17 July 1944, during the Battle of Normandy during World War II, the city was bombed during the Allied offensive against the occupying Germans.

Coutances Cathedral is one of the major buildings of Norman architecture and contains a chapel and stained glass dedicated to Saint Marcouf.

The bishop of Coutances exercised ecclesiastical jurisdiction over the Channel Islands until the Reformation, despite the secular division of Normandy in 1204.