Wareham is an historic market town and, under the name Wareham Town, a civil parish, in the English county of Dorset. The town is situated on the River Frome eight miles (13 km) southwest of Poole.
The town is built on a strategic dry point between the River Frome and the River Piddle at the head of the Wareham Channel of Poole Harbour. The Frome Valley runs through an area of unresistant sand, clay and gravel rocks, and much of its valley has wide flood plains and marsh land. At its estuary the river has formed the wide shallow ria of Poole Harbour. Wareham is built on a low dry island between the marshy river plains.The town's strategic setting has made it an important settlement throughout its long history. Excavations at the nearby Bestwall site have produced evidence of transient early Mesolithic activity dating to around 9000 BCE.
In 1762, a fire destroyed two thirds of the town, which has been rebuilt in Georgian architecture with red brick and Purbeck limestone, following the earlier street pattern. The town is divided into four quarters by the two main roads, which cross at right-angles. The medieval almshouses escaped the fire, and some of the Georgian façades are in fact disguising earlier buildings which also survived.
With the outbreak of the First World War in 1914, Wareham became a garrison town with up to 7,000 soldiers living and training locally. The camp was re-located to nearby Bovington in 1922. The town survived the Second World War largely intact, although five houses were destroyed when a bomb dropped by a German aeroplane fell near St Martin's Church in 1942.
Because of the constraints of the rivers and marshland Wareham grew little during the 20th century, while nearby towns, such as Poole, grew rapidly.
Wareham was allocated the PO Numeral 843 in the post office lists.