Chthamalus (χθαμαλός, "flat" or "on the ground"[2]) is a genus of barnacles that is found along almost all non-boreal coasts of the northern hemisphere, as well as many regions in the southern hemisphere.

These small barnacles have been studied in part because of the taxonomic confusion over a group of species that, by and large, are morphologically and ecologically quite similar.

In recent years, molecular techniques have identified a number of cryptic species that have been subsequently confirmed by taxonomists using morphological measurements.

[4] Identification of barnacles in the field can be challenging, and identification of particular species of Chthamalus is not considered reliable in the field other than a few species.

However, a notable distinction in the arrangement of wall plates can help biologists distinguish Chthamalid barnacles from the other common barnacles in the family Balanidae.