This is a list of the Sites of Special Scientific Interest (SSSIs) in the former county of Avon, England, United Kingdom. In England the body responsible for designating SSSIs is Natural England, which chooses a site because of its fauna, flora, geological or physiographical features. Although the county of Avon no longer exists, Natural England still uses its former borders to mark one of its Areas of Search. As of 2006, there are 86 sites designated in this Area of Search, of which 38 have been designated due to their biological interest, 39 due to their geological interest, and 9 for both.
Natural England took over the role of designating and managing SSSIs from English Nature in October 2006 when it was formed from the amalgamation of English Nature, parts of the Countryside Agency and the Rural Development Service. Natural England, like its predecessor, uses the 1974–1996 county system and as such the same approach is followed here, rather than splitting these sites between the Somerset and Gloucestershire lists. The data in the table is taken from English Nature in the form of citation sheets for each SSSI.
For other counties, see List of SSSIs by Area of Search.