Trebonianus Gallus was one of the many short-lived emperors who ruled the Roman Empire during the turbulent third century. He came to power after the death of Decius in a battle against the Goths, but his reign was marked by military defeats, plague, and civil war. He was eventually killed by his own troops, who preferred another general as emperor.

Trebonianus Gallus was born in 206 AD in Perusia (modern Perugia), Italy. His family had Etruscan origins and a long senatorial tradition. He had a successful political and military career, serving as consul in 245 AD and as governor of Moesia Superior, a province on the Danube frontier, in 250 AD.

In 251 AD, Emperor Decius and his son and co-emperor Herennius Etruscus launched a campaign against the Goths, who had invaded Roman territory and captured many prisoners and plunder. However, the Romans were ambushed and defeated at the Battle of Abrittus, and both Decius and Herennius were killed. Some sources claim that Trebonianus Gallus, who was commanding another army nearby, conspired with the Goths or failed to help Decius, but this is probably an unfounded accusation.

The soldiers of Trebonianus Gallus proclaimed him emperor on the spot, despite the fact that Decius had another son, Hostilian, who was in Rome. Trebonianus Gallus accepted Hostilian as his co-emperor, but also elevated his own son, Volusianus, to the rank of Caesar. He then made peace with the Goths, allowing them to keep their captives and loot and promising them an annual tribute. This was seen as a humiliating and shameful treaty by many Romans, who blamed Trebonianus Gallus for losing the war.

Trebonianus Gallus faced many problems during his brief reign. A devastating plague broke out in Rome and other parts of the empire, killing many people, including Hostilian. The Persian king Shapur I invaded Roman territory in the east and captured several cities. The Franks and the Alamanni crossed the Rhine and raided Gaul and Spain. The Goths resumed their attacks on the Danube provinces. Trebonianus Gallus tried to deal with these threats by sending generals and troops to various fronts, but he lacked the resources and the authority to restore order and security.

In 253 AD, one of his generals, Aemilianus, who had repelled a Gothic invasion in Moesia Inferior, was proclaimed emperor by his soldiers. Trebonianus Gallus marched against him with his son Volusianus, but he was deserted by his own army near Interamna (modern Teramo), Italy. He and his son were killed by their mutinous soldiers, who then joined Aemilianus. Trebonianus Gallus had ruled for only two years and two months.

Trebonianus Gallus is not remembered as a great or successful emperor. He inherited a difficult situation from Decius and failed to improve it. He was unable to stop the external enemies or the internal rivals of Rome. He was also unpopular with the Senate and the people, who resented his peace treaty with the Goths and his persecution of Christians. He was one of the many victims of the crisis of the third century, a period of chaos and decline for the Roman Empire.