The Church of St Mary and St Thomas is a grade I listed building in Knebworth, Hertfordshire, England. The church dates from the twelfth century.
The church is set in a churchyard which has listed tombstones by Edwin Lutyens. It is surrounded by parkland. Archaeological investigations have identified traces of an early settlement between the church and Knebworth House. It is believed that the settlement was abandoned when the park was created in c. 1300.
The architectural historian Nikolaus Pevsner described the exterior of the church as "architecturally insignificant". The most prominent feature is the tower, surmounted by a short spire typical of the region called a "Hertfordshire spike".
Features of interest inside the church include a Norman chancel arch and memorials to the Lytton family.
Coordinates: 51°52′27″N 0°12′48″W / 51.87404°N 0.21347°W