Galerius Valerius Maximinus, born as Daza (20 November c. 270 – c. July 313), was Roman emperor from 310 to 313. He became embroiled in the civil wars of the Tetrarchy between rival claimants for control of the empire, in which he was defeated by Licinius. A committed pagan, he engaged in one of the last persecutions of Christians, before issuing an edict of tolerance near his death.
The emperor Maximinus was originally called "Daza," an ancient name with various unknown high distinction meanings in Illyria, where he was born. He acquired the name "Maximinus" at the request of his maternal uncle, Galerius (a Roman emperor of Dacian and Thracian origin), and his full name as emperor was "Galerius Valerius Maximinus". Modern scholarship often refers to him as "Maximinus Daza."
He was born in the Roman Illyria region to the sister of emperor Galerius near their family lands around Felix Romuliana, in Roman Dacia, a rural area then also in the former Danubian region of Moesia, now modern Eastern Serbia. He rose to high distinction after joining the Roman Army.
In 305, his maternal uncle Galerius became the eastern Augustus and adopted Maximinus as a son and heir, raising him to the rank of Caesar (that is, the junior eastern ruler), and granting him the government of Syria and Egypt.
In 308, after the elevation of Licinius to Augustus, Maximinus and Constantine I were declared filii Augustorum ("sons of the Augusti"), but Maximinus probably started styling himself as Augustus with support of his troops during a campaign against the Sassanids in 310. On the death of Galerius in 311, Maximinus divided the Eastern Empire between Licinius and himself. When Licinius and Constantine I began to make common cause, Maximinus entered into a secret alliance with the usurper Maxentius, who controlled Italy. He came to an open rupture with Licinius in 313; he summoned an army of 70,000 men but sustained a crushing defeat at the Battle of Tzirallum in the neighbourhood of Heraclea Perinthus on 30 April. He fled, first to Nicomedia and afterwards to Tarsus, where he died the following August.
Maximinus' death was variously ascribed "to despair, to poison, and to the divine justice".
Based on descriptions of his death given by Eusebius, and Lactantius as well as the appearance of Graves' ophthalmopathy in a Tetrarchic statue bust from Anthribis in Egypt sometimes attributed to Maximinus, endocrinologist Peter D. Papapetrou has advanced a theory that Maximinus may have died from severe thyrotoxicosis due to Graves' disease