Thoracica is an infraclass of crustaceans which contains the most familiar species of barnacles found on rocky coasts, such as Semibalanus balanoides and Chthamalus stellatus.

They have six well-developed limbs, and may be either stalked or sessile.

The carapace is heavily calcified.

The group includes free-living and commensal species.

[2] This article follows Chan et al. (2021) and WoRMS in placing Thoracica as an infraclass of Thecostraca and in the following classification of thoracicans down to the level of family:[3][4]