Legio III Herculia: one of the legions of the later Roman empire. Its name means "the legion dedicated to Hercules".
III Herculia was probably created to defend a province, but was later added to the field army of Illyricum. The original province is not known, but may have been Raetia. At the end of the fourth century, III Herculia was still part of the Illyrian field army. It is mentioned as the twin of III Italica.