Theodosius was born in Hispania[iv] on 11 January, probably in the year 347.  His father of the same name, Theodosius the Elder was a successful and high-ranking general (magister equitum) under the western Roman emperor Valentinian I, and his mother was called Thermantia.[20] The family appear to have been minor landed aristocrats in Hispania, although it is not clear if this social status went back several generations or if Theodosius the Elder was simply awarded land there for his military service.[21] Their roots to Hispania were nevertheless probably long-standing, since various relatives of the future emperor Theodosius are likewise attested as being from there, and Theodosius himself was ubiquitously associated in the ancient literary sources and panegyrics with the image of fellow Spanish-born emperor Trajan.[22] Theodosius, however, never again visited the Iberian peninsula after becoming emperor.
Very little is recorded of the upbringing of Theodosius. The 5th-century author Theodoret claimed the future emperor grew up and was educated in his Iberian homeland, but his testimony is unreliable. One modern historian instead thinks Theodosius must have grown up among the army, participating in his father's campaigns throughout the provinces, as was customary at the time for families with a tradition of military service.[24] One source says he received a decent education and developed a particular interest in history, which Theodosius then valued as a guide to his own conduct throughout life.
 
Theodosius suffered from a disease involving severe edema. He died in Mediolanum (Milan) on 17 January 395, and his body lay in state in the palace there for forty days.[110] His funeral was held in the cathedral on 25 February.[16] In the presence of Stilicho and Honorius, Bishop Ambrose delivered the panegyric De obitu Theodosii, which praised Theodosius's suppression of paganism.
On 8 November 395, his body was transferred to Constantinople, where according to the Chronicon Paschale he was buried in the Church of the Holy Apostles.[16] He was honored as: Divus Theodosius, lit. 'the Divine Theodosius'. He was interred in a porphyry sarcophagus that was described in the 10th century by Constantine VII Porphyrogenitus in his work De Ceremoniis.