Longworth is a village and civil parish in the Vale of White Horse, England. The 1974 boundary changes transferred it from Berkshire to Oxfordshire. It lies about 7 miles (11 km) west of Abingdon-on-Thames and 9 miles (14 km) south-west of Oxford. The 2011 Census recorded a population of 566, which was estimated at 570 in 2019. The parish is bounded by the River Thames to the north, the A420 road to the south, and field boundaries to the east and west. The land slopes from the A420 to the river, except at Harrowdown Hill near the north-east corner of the parish, which has a summit of 325 feet (99 m).