Alexios I Komnenos, Latinized as Alexius I Comnenus (1056 – 15 August 1118—note that some sources list his date of birth as 1048), is Byzantine emperor from 1081 to 1118, and although he was not the founder of the Komnenian dynasty, it is during his reign that the Komnenos family comes 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 is able to halt 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 are also the catalyst that trigger the Crusades.