Wessex was an Anglo-Saxon kingdom, whose kings eventually conquered the whole of England. Like most Anglo-Saxon realms, it fluctuated in size, but took in much of the south coast of England, from Hampshire to Dorset and into Devon, extending north to the Thames valley. Its most famous king was Alfred the Great.
As a geographical expression, the name was used by Thomas Hardy in his Wessex novels, in which the places of the area were renamed. For instance, Wantage, where Alfred was born, he renamed Alfredston.
The 11th-century title of Earl of Wessex was revived for Prince Edward in 1999.