town and port, unitary authority of Medway, geographic and historic county of Kent, southeastern England, on the River Medway. Gillingham is one of the three Medway towns. Before the establishment of the royal dockyard at nearby Chatham, a portion of the town (known as Grench) was a dependency of Hastings, one of the Cinque Ports. Gillingham was incorporated in 1903 and in 1921 was extended to include Rainham. Many of the inhabitants were employed in the royal dockyard (the greater part of which lay within the borough) until it closed in 1984. The local economy is largely industrial. Pop. (2001) 98,403.