As Camulodunum, the town of Colchester was the capital of the pre-Roman Belgic ruler Cunobelinus and is so named on his coins. Although burned in AD 60 during the rising of the British queen Boudicca, Colchester soon became one of the chief towns in Roman Britain, and surviving relics of this period include walls and gateways. The Saxons called the town Colneceaste; and Domesday Book (1086) mentions it as Colcestra. The town's first charter was given in 1189. Colchester's castle keep (built about 1080) is the largest of its kind in England and now houses a museum of Romano-British antiquities. Holy Trinity Church (1050) has a late Saxon tower, and the Augustinian St. Botolph's Priory retains part of the Norman west front, nave, and arcades. The 13th-century town was a major port. Both Elizabeth I and James I encouraged Flemish weavers to settle there and to manufacture baize fabric, and cloth making still flourishes. The trade in oysters from the River Colne also has a long history.

The borough has picturesque scenery, ranging from the beaches and estuaries on the east coast to the Dedham vicinity, which was often the subject of John Constable's landscapes. Colchester town's industries include printing and the manufacture of electrical equipment, diesel engines, lathes, and bearings. The University of Essex, founded in 1961, is in Colchester. Area 129 square miles (334 square km). Pop. (2001) town, 104,390; borough, 155,794.