The Byzantine civil war of 1373–1379 is a military conflict fought in the East Roman (Byzantine) Empire between Emperor John V Palaiologos and his son, Andronikos IV Palaiologos, also growing into an Ottoman civil war as well, when Savcı Bey, the son of Ottoman Emperor Murad I joins Andronikos in a joint rebellion against their fathers.

It begins when Andronikos seeksto overthrow his father in 1373.

Although he fails, Andronikos is eventually able, with Genoese aid, to overthrow and imprison John V in 1376.

In 1379, however, John V escapes, and with Ottoman help, regains his throne.

The civil war further weakens the declining Empire, which had already suffered several devastating civil wars earlier in the century.

The major beneficiary of the war are the Ottomans, whose vassals the Greeks have effectively become.