Isaac Komnenos or Comnenus was the third son of Byzantine Emperor Alexios I Komnenos and Empress Irene Doukaina. He was raised to the high rank of sebastokrator by his older brother John II Komnenos in reward for his support, but they later fell out, as Isaac began to covet the throne.

Alexios I Komnenos, Latinized Alexius I Comnenus, was Byzantine emperor from 1081 to 1118. Although he was not the first emperor of the Komnenian dynasty, it was during his reign that the Komnenos family came to full power and initiated a hereditary succession to the throne. Inheriting a collapsing empire and faced with constant warfare during his reign against both the Seljuq Turks in Asia Minor and the Normans in the western Balkans, Alexios was able to curb the Byzantine decline and begin the military, financial, and territorial recovery known as the Komnenian restoration. His appeals to Western Europe for help against the Turks was the catalyst that sparked the First Crusade.