ILCHESTER, a town of Somersetshire in England, seated on the river Yeovil. It is a place of great antiquity, as appears by the Roman coins which are sometimes dug up. It once had 16 churches, but now has only two. It is a corporation, and sends two members to parliament; here the county-gaol is kept. W. Long. 2. 45. N. Lat. 51. 5.