Aust Cliff (grid reference ST565894) is a 5.3 hectare geological Site of Special Scientific Interest adjacent to the Severn Estuary, near the village of Aust, South Gloucestershire, notified in 1954.

Its SSSI designation is due to the presence of fossil beds.

The site is famous for its Rhaetic bone bed, and is also the most productive locality in Britain for Triassic insects.

The lower part of the cliff is a red mudstone, with bands of nodules of pinkish-white alabaster.

This article about a Site of Special Scientific Interest in England is a stub.