Hajdú, formerly known as Hajdúság, was an administrative county (comitatus) of the Kingdom of Hungary.
The river Tisza touched its western border.
The Hortobágy National Park steppe lies in the county.
The Hajdúság region had a special status in the Kingdom of Hungary, but was turned into the proper county Hajdú in the 19th century.
[1] In the early 20th century, the subdivisions of Hajdú county were: