The Wilhelminer War is a minor war fought in the March of Pannonia (later Austria) from 882 to 884.

It is initially a rebellion of the sons of the margraves William II and Engelschalk I, led by Engelschalk II, against the new margrave Aribo.

Svatopluk I of Great Moravia intervenes as an ally of Aribo because he had been at war with William and Engelschalk when the two died in 871.

The "Wilhelminers" are the descendants of William I, father of the two late margraves.