Frindsbury is part of the Medway Towns conurbation in Kent, southern England. It lies on the opposite side of the River Medway to Rochester, and at various times in its history has been considered fully or partially part of the City of Rochester. Frindsbury today is part of the town of Strood and covers the most northern part of the town. Frindsbury refers to both a parish and a manor. Within the civil parish of Frindsbury Extra are the villages of Frindsbury, Wainscott, and Upnor. Frindsbury was also the name given to an electoral ward in the City of Rochester that straddled the parishes of Frindsbury and Strood.

Frindsbury lies on the northwest bank of the Medway at its lowest bridging point. After a narrow but marshy coastal strip, the land rises steeply to plateau at about 100 ft (30 m). This was a sheet of chalk covered by brickearth covered with topsoil. Over the last two millennia, much of this was stripped away, or mined, so the contours have constantly changed. Through the centre of this ran a shallow valley carrying a stream draining the Hoo Peninsula behind, through Islingham to Whitewall creek where it entered the Medway. This water flow formed a river meander upstream and a build up of alluvium pushing 1,000 yds into the river. Though rarely more than 25 feet (7.6 m) in height, the Frindsbury peninsula became the centre of many industries. At the Strood end the coastal marsh became 600 yds wide. There is evidence of Roman piling so they could build a road, Watling Street, from Strood Hill across the marsh to the Medway which they bridged. At that time Strood was part of Frindsbury. The impenetrable nature and the steepness of the topography here influenced the route of the railways.