Clunch is a traditional building material used mainly in eastern England. It is a term which encompasses a wide variety of materials, often locally variable.

It often comes as irregular lumps of rock either picked up from the fields, or it may be quarried and hewn from the ground in more regular-shaped building blocks. It is predominately chalk/clay based and is bedded in mortar to form walls.

It is often a very soft limestone. It can be rich in iron-bearing clays or be very fine and white — in effect just chalk. It is used in various parts of East Anglia, where more durable stone is uncommon, and can be seen quite a lot in and around Thetford — mostly now for property boundary walls as it is not a long-lasting material, but it is also used for some building walls, especially in traditional agricultural buildings. In Ely Cathedral it can be seen in some interior locations.

The term is sometimes used more genericly in other parts of England for any soft and aggregate-based vernacular building material which is used as a poor substitute for stone.