County in Hungary before 1919-20 and in western Romania since. It is named after the town of Arad, which is north of Timisoara and east of Szeged, and stands on the River Mures, a tributary of the Tisza. Its name is the same in both Magyar and Romanian.
In the Ottoman era several districts, including Arad, in eastern Hungary, known collectively as the Partium, were joined to the Principality of Transylvania. Though the leadership in Transylvania was Magyar, much of the population was Romanian. Romanians moved westwards into the Partium during this period. As a result Arad had a Magyar majority in the west and a Romanian in the east.
It was ceded by Hungary to Romania in the Treaty of Trianon, 1920.