Arnulf of Carinthia (850 – 8 December 899) was the Carolingian King of East Francia from 887, the disputed King of Italy from 894 and the disputed Holy Roman Emperor from 22 February 896 until his death.

Arnulf was, according to most sources, the illegitimate son of Carloman, King of Bavaria, and his concubine Liutswind, perhaps of Carantanian origin, and possibly the sister of Ernst, Count of the Bavarian Nordgau Margraviate in the area of the Upper Palatinate, or perhaps the burgrave of Passau, as some sources say. After Arnulf's birth, Carloman married, before 861, a daughter of that same Count Ernst, who died after 8 August 879. As it is mainly West-Franconian historiography that speaks of Arnulf's illegitimacy, it is quite feasible that the two females are one and the same person and that Carloman later on actually married Liutswind, thus legitimizing his son.

Arnulf was granted the Duchy of Carinthia, a Frankish vassal state and successor of the ancient Principality of Carantania, by his father Carloman, after Carloman had become reconciled with his own father Louis the German and was created King of Bavaria. Arnulf spent his childhood on the Mosaburch or Mosapurc, which is widely believed to be Moosburg in Carinthia, only a few miles away from one of the Imperial residences, the Carolingian Kaiserpfalz at Karnburg, which before as Krnski grad had been the residence of the Carantanian princes. Arnulf kept his seat here and from later events it may be inferred that the Carantanians, from an early time, treated him as their own Duke. Later, after he had been crowned King of East Francia, Arnulf turned his old territory of Carinthia into the March of Carinthia, a part of the Duchy of Bavaria.