Stratford-sub-Castle in Wiltshire, England, was anciently a separate village and civil parish, but since 1954 has been a northern suburb of the city of Salisbury. At approximately 170 ft above sea level, it is dominated to the east by the remains of an Iron Age hillfort within the boundaries of which a Norman castle was built. This now-ruined castle led to the village taking the name Stratford-under-Castle, later changing to Stratford sub Castle. Stratford lies south-west of the abandoned medieval settlement of Old Sarum which was also built within the area of the hill fort. It is approximately twenty one miles from Southampton.
Stratford sub Castle is within the current city boundaries. There is a primary school; the nearest secondary school to the village is South Wilts Grammar School, a five-minute walk away from the southern boundary of Stratford sub Castle, on Stratford Road.
The oldest building in the area is the Church of St Lawrence, which dates from the 13th century and is a Grade I listed building. The west tower was restored by Thomas Pitt in 1711. A section of the churchyard contains war graves from World War I and World War II that are looked after by the Commonwealth War Graves Commission. Before his conversion to Roman Catholicism, the hymnist Edward Caswall served as a curate.
Stratford-sub-Castle cannot expand to the east or the west, being bounded by Old Sarum on one side and the River Avon on the other: it has thus become a linear settlement.