Herennius Etruscus (Latin: Quintus Herennius Etruscus Messius Decius Augustus; ca. 227 – June 251), was Roman emperor in 251, in a joint rule with his father Decius. Emperor Hostilian was his younger brother.Herennius was born in or near Sirmium in Pannonia (now Sremska Mitrovica, Serbia), during one of his father's military postings. His mother was Herennia Cupressenia Etruscilla, a Roman lady of an important senatorial family.