Hostilian (Latin: Gaius Valens Hostilianus Messius Quintus; died c. July 251) was briefly Roman emperor in 251.

After Decius and Herennius Etruscus, Hostilian's brother, were killed at the Battle of Abritus, an ambush by the Goths, Trebonianus Gallus was proclaimed emperor by the legions.

His full name based on coinage and inscriptions was Gaius Valens Hostilianus Messius Quintus, but to this the historian Aurelius Victor adds Perpenna or Perperna, a name of Etruscan origin.

He defeated and killed Philip in a battle near Verona, after which the Roman Senate confirmed Decius's appointment and honoured him with the name Traianus, a reference to Emperor Trajan.

[2][7][8] In June 251, Decius and Herennius Etruscus were killed by the Goths at the Battle of Abritus, and Trebonianus Gallus was declared emperor.