It is thought that the parish of Rimpton takes its name from its proximity to the boundary of a Saxon estate based at Sherborne. Lying 11 km (7 miles) north east of Yeovil, it is an irregular shape and measures 3 km (2 miles) from north to south and 2 km (1¼ miles) from east to west at its widest point.  The southern boundary mainly follows roads and, with most of the eastern boundary, forms part of the boundary between Somerset and Dorset.

Geologically, the parish lies largely on Pennard sands, silts and marls but the lower ground around the village consists of clay and sandy loam with limestone gravel. Rimpton itself lies on a narrow strip of alluvium formed by a stream, known as Hay or Honey Brook in the 10th century, but as Mill Stream by the 19th century. This flows west and eventually into the River Yeo.

Most of the parish is below the 50 m (164 ft) contour. To the west, the land falls very gradually towards the 30 m (98 ft) contour; in the south and north-east there is a gradual rise, reaching 103m (338 ft) on the southern boundary and 130 m (426 ft) on Corton Ridge in the north-east.  The parish covers 409 ha (1010 acres).