Gyula (Yula, Gula, Gila) was, according to Muslim and Byzantine sources, the title of one of the leaders, the second in rank, of the Hungarian tribal federation in the 9th–10th centuries. In the earliest Hungarian sources, the title name is only recorded as a personal name (Gyyla, Geula, Gyla, Iula).
According to the Hungarian chronicles, Transylvania was ruled by a line of princes called Gyula, and their country was occupied by King Stephen I of Hungary (1000/1001–1038).
The title name has not convincing etymologies, but it is probably of Turkic origin, cf. *yula "torch".
The first data of the title, recorded by Ibn Rusta and Gardizi, can be traced back to the earlier works of Abu Abdallah al-Jayhani. According to these earliest pieces of evidence, the Hungarians were ruled conjointly by two ‘kings’. The major one, called kende (or künde), enjoyed nominal leadership, while effective power was exercised by his colleague, inferior in rank, called the gyula. This peculiar form of governance (‘dual kingship’) is generally supposed to have been imitative of the Khazar Khaganate, which did indeed have a similar organization. However, the only thing that the Muslim sources tell us is that the gyula was in charge of the military matters of the tribal confederation; whereas there existed a legitimate ruler (the kende) who had little influence on army-related issues.
The Majgars are a race of the Turks and their leader rides out with horsemen to the number of 20,000. Their leader is called künde [kende], but this is only a nominal title, for the name of the man who is actually king over them is called jila [jula] and all the Majgars accept the orders of their jila [jula] in the matters of war and defense and the like.
These Majgars are a type of the Turks. Their leader rides out with 20,000 warriors. This leader they call künde [kende]. This is the title of the greater of their kings. That leader who appoints the functionaries they call jula [jole]. What the jula commands, the Majgars do.