Mongewell (first syllable rhymes with "sponge") was formerly a separate parish, but since 1932 simply a village in the civil parish of Crowmarsh, about 1 mile (1.6 km) south of Wallingford in Oxfordshire. Mongewell is on the east bank of the Thames, linked with the west bank by Winterbrook Bridge. The earthwork Grim's Ditch, now part of The Ridgeway long-distance footpath, passes through the northern part of the village and is a scheduled ancient monument.
The ecclesiastical parish was joined by a civil parish in the 19th century, but in 1932 it was split, mostly joining the new civil parish naned Crowmarsh, but a small part added to Rotherfield Greys parish.
For more information, see the EN Wikipedia article Mongewell. A summary of the history of Mongewell Park.