QUEENBOROUGH, a municipal borough in the Faversham parliamentary division of Kent, England, in the Isle of Sheppey, close to the junction of the Swale and Medway, 2 m. S. of Sheerness on the South-Eastern & Chatham railway. Pop. (1901) 1544. The prosperity of the town has been revived in modern times by the establishment by the railway company of a branch line from Sittingbourne in connexion with a service of mail and passenger steamers to Flushing (Holland), which run twice daily. The first copperas factory in England was established at Queenborough in 1579, by Matthias Falconer, of Brabant. In 1890 Portland cement works were built, and there is a large trade in timber. The town is governed by a mayor, 4 aldermen and 12 councillors. Area, 302 acres.
A fortress, called Sheppey Castle, is said to have existed from an early period for guarding the passage of the Swale river. Queenborough Castle was built about 1361 by Edward III., who named the town after Queen Philippa and made it a free borough, with a governing body of a mayor and two bailiffs. Charters were granted by subsequent sovereigns down to Charles I., who reincorporated the town under the title of the mayor, jurats, bailiffs and burgesses of Queenborough. The castle never had any military history, and having been seized by parliament together with the other royal possessions, and being considered of insufficient importance for repair, was demolished during the Commonwealth. The borough subsequently decreased in importance. The chief part of the population were employed in the oyster fishery. The town was first represented in parliament by two members in 1572; it lost its franchise by the Reform Act of 1832.