Hexacorallia is a class of Anthozoa comprising approximately 4,300 species of aquatic organisms formed of polyps, generally with 6-fold symmetry.

It includes all of the stony corals, most of which are colonial and reef-forming, as well as all sea anemones, and zoanthids, arranged within five extant orders.

[2] The hexacorallia are distinguished from another class of Anthozoa, Octocorallia, in having six or fewer axes of symmetry in their body structure; the tentacles are simple and unbranched and normally number more than eight.

Hexacorallia is considered to be monophyletic, that is all contained species are descended from a common ancestor, however it has been suggested that many of the current orders are not.

Historically, Antipatharia was considered to be in a separate class called Ceriantipatharia, though more recent genetic studies place it in Hexacorallia.