Mentioned in Domesday Book (1086) as Givelcestre meaning 'The fort on the River Ivel' from the Old English name of the River Yeo Ivel and Latin castra .

A town with much history, Ilchester, originally called Lindinis (meaning "Little Marsh"), was a strategic Roman fort and major regional settlement (hence ' chester ') on the river Yeo at the important junction of the Fosseway and the Bristol to Dorchester roads (now the A303 and the A37). The Roman levels lie just below the surface within the town and two Roman cemeteries are outside - evidently including both pagan and Christian burials.

During Saxon times there was a mint here (coining money from 959 to 1248) and in Norman times it was a Royal Borough with 107 Burgesses. From 1298 until 1832 the town returned two members to Parliament. Ilchester was a walled and gated town and boasted six churches, a nunnery, friary and a leper hospital in Medieval times. The bridge spanning the Yeo in the town is also Medieval and originally was home to a small chapel for travellers and pilgrims.

It was the County Town of Somerset in the 1700's and the famous Ilchester Gaol - in use from 1166 to 1843 - was home to the County Gaol. The town's past is echoed in the Georgian houses and Town Hall which survive. The church, St Mary Major, with its massive 13th Century tower, is in a mixture of periods and styles; features of interest include a Jacobean pulpit and remains of wall paintings on the north wall of the nave.

The village green to the north of the church boasted an 18th Century Tuscan column. The top portion of this monument was blown over by the storm of 25 January 1991 and rebuilt the following year.