Longstock is in the county of Hampshire in Southern England. It is about 64 miles south west of London and 20 miles north of Southampton sitting midway between the cities of Winchester and Salisbury. The village runs from the upper part of Houghton Road, just across the bridge from Stockbridge, for about 2½ miles (4km) north to Longstock Park.

The village is mainly on the western slope of the Test Valley which runs parallel with the bank of the River Test. The houses are on either side of the road which runs down the bank of the river. See Parish Map below.