Brighton is a seaside resort and one of the two main areas of the City of Brighton and Hove in the county of East Sussex, England. It is located 47 miles south of London. Archaeological evidence of settlement in the area dates back to the Bronze Age, Roman and Anglo-Saxon periods.

Brighton lies between the South Downs and the English Channel to the north and south, respectively. The Sussex coast forms a wide, shallow bay between the headlands of Selsey Bill and Beachy Head; Brighton developed near the centre of this bay around a seasonal river, the Wellesbourne (or Whalesbone), which flowed from the South Downs above Patcham. This emptied into the English Channel at the beach near the East Cliff, forming "the natural drainage point for Brighton".

Behind the estuary was a stagnant pond called the Pool or Poole, so named since the medieval era. This was built over with houses and shops from 1793, when the Wellesbourne was culverted to prevent flooding, and only the name of the road (Pool Valley, originally Pool Lane), marks its site. One original house survives from the time of the pool's enclosure. Behind Pool Valley is Old Steine (historically The Steyne), originally a flat and marshy area where fishermen dried their nets. The Wellesbourne occasionally reappears during times of prolonged heavy rain; author Mark Antony Lower referred to an early 19th-century drawing of the Royal Pavilion showing "quite a pool of water across the Steyne"

Despite 16th-century writer Andrew Boorde's claim that "Bryght-Hempston [is] among the noble ports and havens of the realm",[62] Brighton never developed as a significant port: rather, it was considered as part of Shoreham. Nevertheless, the descriptions "Port of Brighthelmston" or "Port of Brighton" were sometimes used between the 14th and 19th centuries, as for example in 1766 when its notional limits were defined for customs purposes. 

The East Cliff runs for several miles from Pool Valley towards Rottingdean and Saltdean, reaching 24 metres (80 ft) above sea level. The soil beneath it, a mixture of alluvium and clay with some flint and chalk rubble, has experienced erosion for many years. The cliff itself, like the rest of Brighton's soil, is chalk.[6] Below this are thin layers of Upper and Lower Greensand separated by a thicker band of Gault clay. The land slopes upwards gradually from south to north towards the top of the Downs.

Main transport links developed along the floor of the Wellesbourne valley, from which the land climbs steeply—particularly on the east side. The earliest settlement was by the beach at the bottom of the valley, which was partly protected from erosion by an underwater shale-bar. Changes in sea level affected the foreshore several times: 40 acres (16 ha) disappeared in the first half of the 14th century, and the Great Storm of 1703 caused widespread destruction. The first sea defences were erected in 1723, and a century later a long sea wall was built.