Thornbury is a market town and civil parish located in South Gloucestershire in England, approximately 12 miles (19 km) north of the city of Bristol, with a population of 12,342 at the 2001 UK census. The town hosts the headquarters of the South Gloucestershire Council. Its suburbs include the Morton and Thornbury Park districts. The civil parish also includes the hamlet of Milbury Heath. As with the rest of the area surrounding Bristol, Thornbury was in the short-lived County of Avon between 1974 and 1996.
St. Mary's church, begun in the twelfth century with later additions, is the oldest surviving building in the town. The town charter was granted in 1252 by Richard de Clare, Earl of Gloucester and Lord of the Manor of Thornbury. The town grew around the site of its cattle market. Thornbury lost its status as a borough in the 19th century local government reforms, but in 1974 the parish council exercised its new right to designate itself a town council.
The ancient parish of Thornbury covered a large area, extending to the River Severn, and also included Rangeworthy, a detached part of the parish. In 1866 Rangeworthy became a separate civil parish. In 1894 the western part of the parish was separated to create the civil parish of Oldbury-on-Severn, and the eastern part of the parish was separated to create the civil parish of Falfield.
In 1765 Dr John Fewster of Thornbury presented a paper to the Medical Society of London entitled "Cow pox and its ability to prevent smallpox". Fewster was a major influence on his friend and colleague, pioneer of the smallpox vaccine, Edward Jenner.
Thornbury's coat of arms combines the arms of four families important in the town's history: Attwells, Howard, Clare and Stafford. John Attwells left £500 in his will for the establishment of the Free School which merged with the grammar school in 1879. The other three families held the manor at Thornbury over several centuries.
[[Category:Thornbury (hundred), Gloucestershire, England