THETFORD, a market town and municipal borough of England, mostly in the south-western parliamentary division of Norfolk, but partly in the Stowmarket division of Suffolk, 91 m. N.N.E. from London by the Great Eastern railway. Pop. (1901) 4613. The town lies in a level, fertile country at the junction of the river Thet with the Little Ouse. In the time of Edward III. the town had twenty churches and eight monasteries. There are now three churches—St Peter's, St Cuthbert's and St Mary's—principally of Perpendicular flint work; of these St Mary's, on the Suffolk side, is the largest. There are a few monastic remains, the chief) being two gatehouses. The most important relic of antiquity is the Castle Hill, a mound 1000 ft. in circumference and l00 ft. in height. The grammar school was founded in 1610. In King Street is the mansion-house occupied as a hunting-lodge by Queen Elizabeth and James I. The chief public buildings are a gild hall and a mechanics' institute; there are several charities. Brewing and tanning are carried on; and there are also manure and chemical works, brick- and lime-kilns, flour-mills and agricultural implement works, engineering works and iron foundries. The Little Ouse is navigable for barges down to the Great Ouse. Thetford is a suffragan bishopric in the diocese of Norwich. The town is governed by a mayor, 4 aldermen, and 12 councillors. Area, 7096 acres.
Early antiquaries identified Thetford (Theodford, Tetford, Tefford) with Sitomagus, but modern research shows that there is no conclusive evidence of a permanent settlement before the coming of the Angles. Tradition tells that Uffa, who probably threw up the earthworks called the Castle Hill, established the capital of East Anglia here about 575. Thetford owned a royal mint in the 9th century and was a flourishing town when the Conqueror acquired it. Richard I. granted it to Hamelin, Earl Warenne, and when his heirs failed, it merged in the duchy of Lancaster and so in the crown. About 1290 its principal officers were a mayor and coroner, afterwards assisted by eight burgesses, whom Henry VIII. increased to ten. The town, never very prosperous since the Conquest, had then fallen into great decay, but the petitions of the burgesses for a charter were not heeded till 1573 when Elizabeth incorporated it under a mayor and common council. This charter, restored in 1692 after its surrender to Charles II., remained in force till 1835 when the borough was re-constituted. Thetford returned two members to parliament from 1529 till its disfranchisement in 1868. Its Saturday market, which certainly existed in the 13th century, was granted by the charter of 1573 and also a Magdalen fair (the 22nd of July). Fisheries were important in the 13th century.
See A. L. Hunt, Capital of East Anglia (1870); T. Martin, History of Thetford (1779).