Publius Licinius Egnatius Gallienus (c. 218 – September 268) was Roman emperor with his father Valerian from 253 to 260 and alone from 260 to 268. He ruled during the Crisis of the Third Century that nearly caused the collapse of the empire. He won numerous military victories against usurpers and Germanic tribes, but was unable to prevent the secession of important provinces. His 15-year reign was the longest in half a century.
 
Cecropius, commander of the Dalmatians, spread the word that the forces of Aureolus were leaving the city, and Gallienus left his tent without his bodyguard, only to be struck down by Cecropius.[52] One version has Claudius selected as emperor by the conspirators, another chosen by Gallienus on his death bed; the Historia Augusta was concerned to substantiate the descent of the Constantinian dynasty from Claudius, and this may explain its accounts, which do not involve Claudius in the murder. The other sources (Zosimus i.40 and Zonaras xii.25) report that the conspiracy was organized by Heraclianus, Claudius, and Aurelian.
According to Aurelius Victor and Zonaras, on hearing the news that Gallienus was dead, the Senate in Rome ordered the execution of his family (including his brother Valerianus and son Marinianus) and their supporters, just before receiving a message from Claudius to spare their lives and deify his predecessor. The tomb of Gallienus is thought to be located to the south of Rome, at the IXth mile of the Via Appia.