Somerset is a historic county in the south west of England. There is evidence of human occupation since prehistoric times with hand axes and flint points from the Palaeolithic and Mesolithic eras, and a range of burial mounds, hill forts and other artefacts dating from the Neolithic, Bronze and Iron Ages. The oldest dated human road work in Great Britain is the Sweet Track, constructed across the Somerset Levels with wooden planks in the 39th century BCE.

Following the Roman Empire's invasion of southern Britain, the mining of lead and silver in the Mendip Hills provided a basis for local industry and commerce. Bath became the site of a major Roman fort and city, the remains of which can still be seen. During the Early Medieval period Somerset was the scene of battles between the Anglo-Saxons and first the Britons and later the Danes. In this period it was ruled first by various kings of Wessex, and later by kings of England. Following the defeat of the Anglo-Saxon monarchy by the Normans in 1066, castles were built in Somerset.

Expansion of the population and settlements in the county continued during the Tudor and more recent periods. Agriculture and coal mining expanded until the 18th century, although other industries declined during the industrial revolution. In modern times the population has grown, particularly in the seaside towns, notably Weston-super-Mare. Agriculture continues to be a major business, if no longer a major employer because of mechanisation. Light industries are based in towns such as Bridgwater and Yeovil. The towns of Taunton and Shepton Mallet manufacture cider, although the acreage of apple orchards is less than it once was.

Palaeolithic and Mesolithic The Palaeolithic and Mesolithic periods saw hunter-gatherers move into the region of Somerset. There is evidence from flint artefacts in a quarry at Westbury that an ancestor of modern man, possibly Homo heidelbergensis, was present in the area from around 500,000 years ago. There is still some doubt about whether the artefacts are of human origin but they have been dated within Oxygen Isotope Stage 13 (524,000 – 478,000 BP). Other experts suggest that "many of the bone-rich Middle Pleistocene deposits belong to a single but climatically variable interglacial that succeeded the Cromerian, perhaps about 500,000 years ago. Detailed analysis of the origin and modification of the flint artefacts leads to the conclusion that the assemblage was probably a product of geomorphological processes rather than human work, but a single cut-marked bone suggests a human presence." Animal bones and artefacts unearthed in the 1980s at Westbury-sub-Mendip, in Somerset, have shown evidence of early human activity approximately 700,000 years ago.

Homo sapiens sapiens, or modern man, came to Somerset during the Early Upper Palaeolithic. There is evidence of occupation of four Mendip caves 35,000 to 30,000 years ago.The Archaeology of Somerset by C Webster and T Mayberry During the Last Glacial Maximum, about 25,000 to 15,000 years ago, it is probable that Somerset was deserted as the area experienced tundra conditions. Evidence was found in Gough's Cave of deposits of human bone dating from around 12,500 years ago. The bones were defleshed and probably ritually buried though perhaps related to cannibalism being practised in the area at the time or making skull cups or storage containers. Somerset was one of the first areas of future England settled following the end of Younger Dryas phase of the last ice age c. 8000 BC. Cheddar Man is the name given to the remains of a human male found in Gough's Cave in Cheddar Gorge. He is Britain's oldest complete human skeleton. The remains date from about 7150 BC, and it appears that he died a violent death. Somerset is thought to have been occupied by Mesolithic hunter-gatherers from about 6000 BCE; Mesolithic artefacts have been found in more than 70 locations. Mendip caves were used as burial places, with between 50 and 100 skeletons being found in Aveline's Hole. In the Neolithic era, from about 3500 BCE, there is evidence of farming.

At the end of the last ice age the Bristol Channel was dry land. However, the sea level later rose, particularly between 1220 and 900 BC and between 800 and 470 BCE, resulting in major coastal changes. The Somerset Levels became flooded, but the dry points such as Glastonbury and Brent Knoll have a long history of settlement, and are known to have been occupied by Mesolithic hunters. The county has prehistoric burial mounds (such as Stoney Littleton Long Barrow), stone rows (such as the circles at Stanton Drew and Priddy) and settlement sites. Evidence of Mesolithic occupation has come both from the upland areas, such as in Mendip caves, and from the low land areas such as the Somerset Levels. Dry points in the latter such as Glastonbury Tor and Brent Knoll, have a long history of settlement with wooden trackways between them. There were also "lake villages" in the marsh such as those at Glastonbury Lake Village and Meare. One of the oldest dated human road work in Britain is the Sweet Track, constructed across the Somerset Levels with wooden planks in the 39th century BC, partially on the route of the even earlier Post Track.

Neolithic, Bronze and Iron Ages

There is evidence of Exmoor's human occupation from Mesolithic times onwards. In the Neolithic period people started to manage animals and grow crops on farms cleared from the woodland, rather than act purely as hunter gatherers. It is also likely that extraction and smelting of mineral ores to make tools, weapons, containers and ornaments in bronze and then iron started in the late Neolithic and into the Bronze and Iron Ages.

The caves of the Mendip Hills were settled during the Neolithic period and contain extensive archaeological sites such as those at Cheddar Gorge. There are numerous Iron Age Hill Forts, which were later reused in the Dark Ages, such as Cadbury Castle, Worlebury Camp and Ham Hill. The age of the henge monument at Stanton Drew stone circles is unknown, but is believed to be from the Neolithic period. There is evidence of mining on the Mendip Hills back into the late Bronze Age when there were technological changes in metal working indicated by the use of lead. There are numerous "hill forts", such as Small Down Knoll, Solsbury Hill, Dolebury Warren and Burledge Hill, which seem to have had domestic purposes, not just a defensive role. They generally seem to have been occupied intermittently from the Bronze Age onward, some, such as Cadbury Camp at South Cadbury, being refurbished during different eras. Battlegore Burial Chamber is a Bronze Age burial chamber at Williton which is composed of three round barrows and possibly a long, chambered barrow.

The Iron Age tribes of later Somerset were the Dobunni in north Somerset, Durotriges in south Somerset and Dumnonii in west Somerset. The first and second produced coins, the finds of which allows their tribal areas to be suggested, but the latter did not. All three had a Celtic culture and language. However, Ptolemy stated that Bath was in the territory of the Belgae, but this may be a mistake. The Celtic gods were worshipped at the temple of Sulis at Bath and possibly the temple on Brean Down. Iron Age sites on the Quantock Hills, include major hill forts at Dowsborough and Ruborough, as well as smaller earthwork enclosures, such as Trendle Ring, Elworthy Barrows and Plainsfield Camp.

Roman

Somerset was part of the Roman Empire from 47 AD to about 409 AD. However, the end was not abrupt and elements of Romanitas lingered on for perhaps a century.

Somerset was invaded from the south-east by the Second Legion Augusta, under the future emperor Vespasian. The hillforts of the Durotriges at Ham Hill and Cadbury Castle were captured. Ham Hill probably had a temporary Roman occupation. The massacre at Cadbury Castle seems to have been associated with the later Boudiccan Revolt of 60–61 AD. The county remained part of the Roman Empire until around 409 AD.

The Roman invasion, and possibly the preceding period of involvement in the internal affairs of the south of England, was inspired in part by the potential of the Mendip Hills. A great deal of the attraction of the lead mines may have been the potential for the extraction of silver.

Forts were set up at Bath and Ilchester. The lead and silver mines at Charterhouse in the Mendip Hills were run by the military. The Romans established a defensive boundary along the new military road known the Fosse Way (from the Latin fossa meaning ditch). The Fosse Way ran through Bath, Shepton Mallet, Ilchester and south-west towards Axminster. The road from Dorchester ran through Yeovil to meet the Fosse Way at Ilchester. Small towns and trading ports were set up, such as Camerton and Combwich. The larger towns decayed in the latter part of the period, though the smaller ones appear to have decayed less. In the latter part of the period, Ilchester seems to have been a "civitas" capital and Bath may also have been one. Particularly to the east of the River Parrett, villas were constructed. However, only a few Roman sites have been found to the west of the river. The villas have produced important mosaics and artifacts. Cemeteries have been found outside the Roman towns of Somerset and by Roman temples such as that at Lamyatt. Romano-British farming settlements, such as those at Catsgore and Sigwells, have been found in Somerset. There was salt production on the Somerset Levels near Highbridge and quarrying took place near Bath, where the Roman Baths gave their name to Bath.

Excavations carried out before the flooding of Chew Valley Lake also uncovered Roman remains, indicating agricultural and industrial activity from the second half of the 1st century until the 3rd century AD. The finds included a moderately large villa at Chew Park, where wooden writing tablets (the first in the UK) with ink writing were found. There is also evidence from the Pagans Hill Roman Temple at Chew Stoke. In October 2001 the West Bagborough Hoard of 4th century Roman silver was discovered in West Bagborough. The 681 coins included two denarii from the early 2nd century and 8 Miliarense and 671 Siliqua all dating to the period AD 337 – 367. The majority were struck in the reigns of emperors Constantius II and Julian and derive from a range of mints including Arles and Lyon in France, Trier in Germany and Rome.

In April 2010, the Frome Hoard, one of the largest-ever hoards of Roman coins discovered in Britain, was found by a metal detectorist. The hoard of 52,500 coins dated from the 3rd century AD and was found buried in a field near Frome, in a jar below the surface. The coins were excavated by archaeologists from the Portable Antiquities Scheme.

Sub-Roman period