Somerset ( (listen) SUM-ər-sit, -⁠set; archaically Somersetshire SUM-ər-sit-sheer, -⁠set-, -⁠shər) is a ceremonial county in South West England which borders Gloucestershire and Bristol to the north, Wiltshire to the east, Dorset to the south-east and Devon to the south-west. It is bounded to the north and west by the Severn Estuary and the Bristol Channel, its coastline facing southeastern Wales. Its traditional border with Gloucestershire is the River Avon.

Between 1889 and 2023, most of the county was administered by Somerset County Council under a two-tier system. In 1974, the county's northern areas became part of the newly formed County of Avon, later returning to Somerset again in 1996, albeit under the separate administration of two new unitary authorities, North Somerset and Bath and North East Somerset. The rest of the county retained a two-tier system – with the ceremonial county as a whole being formed of six council areas from 2019, of which two were the aforementioned northern unitary authorities – until 1 April 2023, when it too became unitarised, and the four last surviving second-tier district councils merged, under the now Somerset Council; since then, the county has comprised three unitary authorities. Its county town is Taunton.

Somerset is a rural county of rolling hills, the Blackdown Hills, Mendip Hills, Quantock Hills and Exmoor National Park, and large flat expanses of land including the Somerset Levels. There is evidence of human occupation from Paleolithic times, and of subsequent settlement by the Celts, Romans and Anglo-Saxons. The county played a significant part in Alfred the Great's rise to power, and later the English Civil War and the Monmouth Rebellion. The city of Bath is famous for its Georgian architecture and is a UNESCO World Heritage Site.