Isbul (fl. 820s–830s) is the kavhan, or first minister, of the First Bulgarian Empire during the reigns of Omurtag, Malamir and Presian I.

Appointed to the kavhan office under Omurtag, Isbul is a regent or co-ruler of the underage Malamir and his successor Presian.

Under Malamir and Presian, Isbul heads Bulgaria's successful campaigns against the Byzantines in southern Thrace and Macedonia, which leads to a significant territorial expansion of the Bulgarian realm.

As a co-ruler of Malamir, Isbul also finances the construction of a water conduit in the capital Pliska.

As second-in-command, Isbul holds enormous power and wealth, and is unusually often mentioned beside the name of the ruler in inscriptions.

Due to his merits, Isbul has been described by historians as an architect of medieval Bulgarian statehood.