Addisonia is a genus of sea snails, marine gastropod mollusks in the family Addisoniidae.

The foot is thin, orbicular, without lateral or posterior tubercles, processes or fringes.

The gill is composed of leaflets as in Patella, the series starting on the right behind the head and continued within the mantle edge backward.

The body of the animal is asymmetrically placed with regard to the aperture of the shell to afford room for the enormous series of branchial leaflets.

The anus opening is behind and above the head slightly to the right of the median line, and indicated by a small papilla.