Medway is a unitary authority area with borough status in the ceremonial county of Kent in South East England. It was formed in 1998 by merging the boroughs of Rochester-upon-Medway and Gillingham, and is administered by Medway Council, which is independent from Kent County Council. The borough had a population of 278,016 in 2019. The borough contains the towns of Chatham, Gillingham, Rainham, Rochester and Strood, which are collectively known as the Medway Towns.

Medway is one of the boroughs included in the Thames Gateway development scheme. It is also the home of Universities at Medway, a tri-partite collaboration of the University of Greenwich, the University of Kent and Canterbury Christ Church University on a single campus in Chatham, together with the Medway School of Arts.

Because of its strategic location by the major crossing of the River Medway, the borough has made a wide and significant contribution to Kent, and to England, dating back thousands of years, as evident in the siting of Watling Street by the Romans and by the Norman Rochester Castle, Rochester Cathedral (the second oldest in Britain) and the Chatham naval dockyard and its associated defences.

The main towns in the conurbation are (from west to east): Strood, Rochester, Chatham, Gillingham, and Rainham. These are traditionally known as the Medway Towns. Many other towns and villages such as Frindsbury and Brompton lie within the conurbation. Outside the urban area, the villages retain parish councils. Cuxton, Halling and Wouldham are in the Medway Gap region to the south of Rochester and Strood. Hoo St Werburgh, Cliffe, High Halstow, St Mary Hoo, Allhallows, Stoke and Grain are on the Hoo Peninsula to the north. Frindsbury Extra including Upnor borders Strood.

The southern part of the urban area is on the north slope of the North Downs, including the suburbs of Walderslade, Luton, Hempstead and Wigmore.

Over half of the unitary authority area is rural in nature. Medway includes parts of the North Kent Marshes, an environmentally significant wetlands region with several Sites of Special Scientific Interest (SSSIs). Other similar areas of conservation include Ranscombe Farm on chalk grassland and woodland between Strood and Cuxton, with rare woodland flowers and orchids.

The Medway area has a long and varied history dominated originally by the city of Rochester and later by the naval and military establishments principally in Chatham and Gillingham.

Rochester was established on an Iron Age site by the Romans, who called it Durobrivae (meaning "stronghold by the bridge"), to control the point where Watling Street (now the A2) crossed the River Medway. Rochester later became a walled town and, under later Saxon influence, a mint was established here. The first cathedral was built by Bishop Justus in 604 and rebuilt under the Normans by Bishop Gundulf, who also built the castle that stands opposite the cathedral. Rochester was also an important point for people travelling the Pilgrims' Way, which stretches from Winchester to the shrine of Thomas Becket at Canterbury. The Pilgrims' Way crossed the Medway near Cuxton.