Totternhoe Stone is a relatively hard chalk outcropping in the middle of the Lower Chalk in the Chiltern Hills in Hertfordshire, Buckinghamshire, Bedfordshire and Cambridgeshire, England. Geologically, it is located in the upper part of the Cenomanian stage of the Cretaceous.
Unusually among chalks, it is sufficiently strong for use as a building stone, and has been used as such in these localities, notably in Woburn Abbey, Luton parish church and several smaller local churches. It weathers rather badly in external use, but when used as internal carved decoration, it has remained in good condition for centuries. Old decorative carving is to be found in St Albans Abbey and in the altar screen of Westminster Abbey.
The Totternhoe Stone is underlain by the argillaceous Chalk Marl. Above is the less argillaceous Grey Chalk. The bed varies in thickness from 0.5 to 5 metres. The stone, although fine-grained, is siliceous, and partial cementing with silica accounts for its relative hardness. It forms a distinct escarpment at several locations at the base of the Chiltern ridge, notably at Totternhoe, Bedfordshire 51°53′24″N 0°34′34″W / 51.89°N 0.576°W, where it is at its thickest. In addition to use as a building stone, in the past it was used in the manufacture of a hydraulic lime, and in cement manufacture at three cement plants.