Coordinates: 51°22′45″N 0°32′59″E / 51.3792°N 0.5498°E / 51.3792; 0.5498

Gillingham ⁱ/ˈdʒɪlɪŋəm/ is a town in the unitary authority of Medway in South East England. It is part of the ceremonial county of Kent. The town includes the settlements of Brompton, Hempstead, Wigmore, Parkwood ,Rainham, Rainham Mark and Twydall.

Gillingham means a homestead of Gylla's family, from Old English ham (village, homestead) and ingas (family, followers), and was first recorded in 10th century as Gyllingeham.

Also referred to in old texts as Jillyingham Water, hence the pronunciation being Gillingham (the G sounds as a "J" as in the girls' name Jill).

Gillingham became an urban district under the Local Government Act 1894, gaining municipal borough status in 1903. John Robert Featherby was the first mayor of the Borough of Gillingham. In 1928 Rainham was added to the Gillingham Borough. Under the Local Government Act 1972 it became a non-metropolitan district. It merged with the other Medway towns (in the City of Rochester-upon-Medway district) in 1998 under the 1990s UK local government reform, to become part of the Medway unitary authority.