Bihor County is a county (județ) in western Romania. With a total area of 7,544 km2 (2,913 sq mi), Bihor is Romania's 6th largest county geographically and the main county in the historical region of Crișana. Its capital city is Oradea.

Crișana is a geographical and historical region in north-western Romania, named after the Criș (Körös) River and its three tributaries: the Crișul Alb, Crișul Negru, and Crișul Repede. In Romania, the term is sometimes extended to include areas beyond the border, in Hungary; in this interpretation, the region is bounded to the east by the Apuseni Mountains, to the south by the Mureș River, to the north by the Someș River, and to the west by the Tisza River, the Romanian-Hungarian border cutting it in two. However, in Hungary, the area between the Tisza River and the Romanian border is usually known as Tiszántúl.