Highworth is situated atop a hill overlooking the upper Thames valley, a few miles from Swindon; its position the highest town in Wiltshire was apparently long considered to have strategic value, for the hill attracted settlement from Mesolithic times, initially around springs emerging from the hillside. A small Saxon village there was the central component of the hundred of Worth (a Saxon word for a settlement), to which the term 'High' was sometimes added to distinguish the settlement, perhaps once it had become a town. The hundred in turn was part of the royal manor of Sevenhampton; it appears that Highworth may have been another example of the royal estate centres of the Saxon period. Highworth was flanked by two outlying Domesday villages: Estrop to the east and Westrop to the north-west, which contributed to the consumer and producer base. A church possibly the mother-church of the hundred was established on the crest of the ridge in Highworth before the time of Domesday and by 1091 it belonged to Salisbury cathedral, which had it rebuilt; in the taxation of 1291 it had the highest value of any church in Wiltshire, and its relatively high valuation in Domesday suggests it of some local importance then (i.e. possibly a minster).
Licence for a Wednesday market and late September fair were acquired in 1206 by Warin Fitz-Gerold, Knight Templar, hereditary chamberlain of the Exchequer, and a capable servant of King John; by 1206 he in his own right and through his marriage to Alice the widow of leading Londoner Henry de Cornhill, and joint heiress of the Somerset-based de Courcy family already held lands in several counties. In 1209 he obtained a licence for a market and fair for Harewood (Yorks.), one of the de Courcy properties, and apparently established a town in conjunction, for the charter granting the market also allowed that Harewood should have all the liberties and free customs possessed by the borough of Richmond; by 1269 Harewood shows evidence of burgesses. Warin's daughter Margaret would in 1242 defend Harewood's market with a challenge to the Knights Templar market at Wetherby, licensed in 1240. Warin's brother Henry was even more active in his sphere: in 1215 he was granted a market and fair for his manor of Campton (Beds.); three years later he had grant of a market at Kemberton (Gloucs.) and just a couple of weeks later received grant of a market at Baulking (Berks.), though within a few months changed its day, perhaps in consequence of a challenge, or competition, from an older market, and his son added a fair in 1254; in 1229 Henry acquired a market licence for Shefford (then Shipford, Beds.), probably to re-establish, on a different day, a market (possibly unlicensed, although Henry's son later claimed King John had issued a grant) that had been challenged in 1225 as detrimental to the king's market at Bedford, and likely shut down as a result. Henry's son took out licences for Kingston Lisle (Berks.) and Mursley (Bucks.).
Warin Fitz-Gerold's daughter Margaret, heiress to most of his properties, married a son of William de Redvers, 5th earl of Devon, and bore the 6th earl, Baldwin de Redvers. It was the latter's son, the 7th earl, under the alias of Baldwin de Insula, who took out in 1257 a licence for a second fair at Highworth, for early August. In 1262 we have the first documentary confirmation of the existence of a town, in the mention of fifty tenants of burgage properties there, and in 1298 it was invited as a borough to send representatives to parliament. While the Fitz-Gerold/Redvers family may have been interested in developing Highworth as a source of revenue, a sister of the 7th earl inherited, and she granted the manor in 1276 to Adam de Stratton (an unscrupulous Wiltshire moneylender who obtained the manor by serving as deputy to the Countess of Devon in her role as king's chamberlain) and, after his disgrace in the 1290s, it fell to a series of royal keepers.
The marketplace was the core of the medieval town and the medieval property boundaries, with narrow frontages, remain a distinctive characteristic, although besides the church very little of the medieval building fabric survives. A road from the north-east (from Chipping Faringdon, Berks., which would obtain a market licence in 1218) passed through Estrop before swinging north-westwards to the church of Highworth, where it traversed the south side of the churchyard; on the other side of the churchyard it met a north-south road, connecting to Swindon and Lechlade, that passed by Westrop. The marketplace was a large funnel-shaped space on the east side of the churchyard, a widening of the final stretch of the east-west road (now the High Street), with a central portion of the medieval marketplace escaping infilling to survive today in that capacity); the market may also have overflowed along the street on the south side of the churchyard, partly infilled before the close of the Middle Ages. The planned town looks to have been laid out to north and south of the marketplace, with the larger southern section spreading westwards to the edge of the north-south road.
Taxation data from the fourteenth century suggest that Highworth's prosperity increased, relative to other villages in the region; perhaps its somewhat isolated position gave a little protection from the worst of the outbreaks of plague. Despite this there is little sign the town underwent any expansion in the Late Middle Ages, although population growth may have been absorbed by marketplace infilling together with expansion of Estrop and Westrop. The cloth trade is evidenced by the presence in Highworth of mercers, fullers, and dyers, while in 1365 we hear of a shop there known as the Shereresshoppe. It remained only a small market town, yet was one of the more important ones in that region of Wiltshire by the late sixteenth century, with a population surpassing that of Swindon, though in later centuries it would decline.