Octocorallia (also known as Alcyonaria) is a class of Anthozoa comprising over 3,000 species[1] of marine organisms formed of colonial polyps with 8-fold symmetry.

The channels interconnect the gastrovascular cavities of the polyps, allowing water and nutrients to flow freely between all the members of the colony.

The pharynx is surrounded by eight radial partitions, or mesenteries, that divide the upper part of the gastrovascular cavity into chambers, one of which connects to the hollow space inside each tentacle.

[10] Octocorallia is considered to be monophyletic, meaning that all contained species are descended from a common ancestor, but the relationships between subdivisions are not well known.

The following taxa are unplaced within Octocorallia according to the World Register of Marine Species as of April 2024[update]:[11] Families: Genera: