Old St Mary's, Walmer, St Mary's Old Church, Blessed Mary of Walmer is a grade II* listed church in Upper Walmer, Kent, United Kingdom.
It was built in 1120 as the chapel to the adjoining Walmer Manor (now in ruins). The original Norman entrance door and chancel arch survive, along with two windows on the south side. However, the nave's north wall was removed early in the 19th century to build on an extension, in which the Duke of Wellington worshipped whilst staying at Walmer Castle as Lord Warden of the Cinque Ports. His hatchment hangs on the north wall, which was reinstated in its original position when the extension was demolished in 1898 after the new churches of St Saviour's and New St Mary's had been built in the parish (Old St Mary's had previously been the parish's only church).
Coordinates: 51°12′11.5″N 1°23′13″E / 51.203194°N 1.38694°E