Warnham SSSI is a 28.5-hectare (70-acre) geological Site of Special Scientific Interest north of Horsham in West Sussex.

[1][2] It is a Geological Conservation Review site.

[3] This site exposes rocks of the Weald Clay Group, dating to the Lower Cretaceous around 130 million years ago.

It preserves fossil plants from freshwater and brackish-marine environments.

[4] The site is private land with no public access.