Hadrian was born in Spain. When his father died his guardian became his cousin, Trajan, who became emperor in 98. Hadrian served as consul under Trajan's reign and succeeded him in 117. He was a follower of the Stoic philosophy.

His cosmopolitan outlook led him to travel around the empire. During this journeys he strengthened fortifications to secure the frontiers of the empire. He reversed the expansionist policies in a permanent shift to the defensive.

In 134 he supressed a rebellion of the Jews in Palestine. At home he instructed jurists to draw up a legal code, a code which was the basis of the Justinian code that became the basis of much of Europe's legal system.