Marcus Clodius Pupienus Maximus and Decius Caelius Calvinus Balbinus (both died on July 29, 238) were elected co-emperors by the Roman senate on April 22, 238 after the failure of Gordian I and Gordian II to defeat the usurper Maximinus Thrax.
Pupienus, born about 178, was an example of ascension in the Roman hierarchical system due to military success. He started as a primus pilus and became a military tribune, praetor, consul (twice) and governor of several Roman provinces including the troublesome Germania Inferior. In 234 he was prefect of Rome and gained a reputation for severity.
Balbinus had an equal share of consular status and political clout. As with Pupienus, he belonged to a special senatorial commission to deal with the problem of Maximinus Thrax. The usurper emperor had been declared a public enemy and, after the defeat in Africa of the senate's candidates, Gordian I and Gordian II, was marching on Rome. Without other candidates in view, the senate elected Pupienus and Balbinus joint emperors. The grandson of Gordian I and future Gordian III was nominated Caesar to appease the population of Rome. Pupienus was sent at the head of an army to face Maximinus, and Balbinus stayed in Rome.
Meanwhile, Maximinus' situation was not easy. Discontentment due to lack of supplies and the strong opposition of the senate, forced his legionaries to rethink their allegiance. Soldiers of the Legio II Parthica killed the usurper and surrendered to Pupienus in the end of June. The co-emperor then returned to Rome, only to find the city in riot. Balbinus had not managed to control the situation and the city had burned in a fire resulting in mutiny. With both emperors present, the situation calmed down but the unease remained.
The relation between Balbinus and Pupienus had been clouded with suspicion from the start, with both fearing an assassination from the other. They were planning an enormous double campaign, Pupienus against the Parthians and Balbinus against the Germanic tribes, but they quarrelled frequently. It was during one of these heavy discussions, on July 29, that the Praetorian guard decided to intervene. They stormed into the room containing the emperors and killed them both. On the same day, Gordian III, only 13 years old, was proclaimed emperor.
Together they ruled a little more than three months. Coins from their short reign show one of them on one side and two clasped hands on the other to show their joint power.