Cassington is a village and civil parish in Oxfordshire about 5 miles (8 km) northwest of Oxford. The village lies on gravel strata about 1⁄2 mile (800 m) from the confluence of the River Evenlode with the River Thames. The parish includes the hamlet of Worton northeast of the village and the site of the former hamlet of Somerford to the south. Somerford seems to have been abandoned early in the 14th century. Cassington is formed of two parts, "upper" and "lower", each with its own village green. The 2011 Census recorded the parish's population as 750.

The River Evenlode is a tributary of the Thames in Oxfordshire. It rises near Moreton-in-Marsh, Gloucestershire, in the Cotswold Hills and flows south-east to the Thames, its valley providing the route of the southern part of the Cotswold Line. The river flows for 45 miles (72 km) from source to the River Thames.