Isaac Komnenos or Comnenus (, Isaakios Komnenos; 16 January 1093 – after 1152) was the third son of Byzantine Emperor Alexios I Komnenos (r. 1081–1118) and Empress Irene Doukaina. He was raised to the high rank of sebastokrator by his older brother John II Komnenos, but they later fell out and Isaac was exiled by John for several years. During the struggle for John's succession in 1143, he supported the unsuccessful candidacy of his nephew, likewise named Isaac, over the younger Manuel I Komnenos. A few years later, he was forced to retire to a monastery by Manuel. Isaac was noted for his erudition and his patronage of learning.