Wombarra Claystone is a geologic formation in the Sydney Basin in eastern Australia.

Commonly seen in the Illawarra region, this stratum is up to 30 metres thick.

Formed in the late Permian to the early Triassic, it is part of the Narrabeen Group of sedimentary rocks.

This formation includes grey shale, and minor quartz-lithic sandstone.

This article about a specific Australian geological feature is a stub.