The Battle of Mauropotamos is fought in 844, between the armies of the Byzantine Empire and the Abbasid Caliphate, at Mauropotamos (either in northern Bithynia or in Cappadocia).

After a failed Byzantine attempt to recover the Emirate of Crete in the previous year, the Abbasids launch a raid into Asia Minor.

The Byzantine regent, Theoktistos, heads the army that goes to meet the invasion but is heavily defeated, and many of his officers defect to the Arabs.

Internal unrest prevents the Abbasids from exploiting their victory, however.

A truce and a prisoner exchange are consequently agreed in 845, followed by a six-year cessation of hostilities, as both powers focus their attention elsewhere.