Komnenos (Greek: ; Latinized Comnenus; plural Komnenoi or Comneni (, [komnini])) was a Byzantine Greek noble family who ruled the Byzantine Empire from 1081 to 1185, and later, as the Grand Komnenoi (, Megalokomnenoi) founded and ruled the Empire of Trebizond (12041461). Through intermarriages with other noble families, notably the Doukai, Angeloi, and Palaiologoi, the Komnenos name appears among most of the major noble houses of the late Byzantine world.

Alexios I Komnenos (Greek: Ἀλέξιος Κομνηνός, 1057 – 15 August 1118), Latinized Alexius I Comnenus, was Byzantine emperor from 1081 to 1118. Although he was not the founder of the Komnenian dynasty, it was during his reign that the Komnenos family came to full power. 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. The basis for this recovery were various reforms initiated by Alexios. His appeals to Western Europe for help against the Turks were also the catalyst that contributed to the convoking of the Crusades.