Quintus Herennius Decius: son and co-ruler of the Roman emperor Decius (r. 250-251).
- c.220-230: Quintus Herennius Etruscus Messius Decius
- May 250: caesar; Princeps Iuventutis
- June 251: Imperator Caesar Quintus Herennius Etruscus Messius Decius Augustus
- July 251: killed in action
Successor of: Decius
Appointed by his father Decius as co-ruler, but killed in a fight near Abritus in Moesia. His father died soon after but Hostilianus, a younger son was adopted by Trebonianus Gallus. This young man soon died of natural causes.