Białystok County (Polish: powiat białostocki) is a unit of territorial administration and local government (powiat) in Podlaskie Voivodeship, north-eastern Poland, on the border with Belarus. It was created on January 1, 1999 as a result of the Local Government Reorganization Act of 1998. Its administrative seat is the city of Białystok, although the city is not part of the county (it constitutes a separate city county). The county contains eight towns: Łapy, 25 km (16 mi) south-west of Białystok, Czarna Białostocka, 22 km (14 mi) north of Białystok, Wasilków, 11 km (7 mi) north of Białystok, Choroszcz, 13 km (8 mi) west of Białystok, Supraśl, 16 km (10 mi) north-east of Białystok, Zabłudów, 16 km (10 mi) south-east of Białystok, Tykocin, 29 km (18 mi) west of Białystok, and Suraż, 23 km (14 mi) south-west of Białystok.
The county covers an area of 2,984.64 square kilometres (1,152.4 sq mi), making it the largest county in Poland (ahead of Olsztyn County). As of 2006 its total population is 136,797, out of which the population of Łapy is 16,583, that of Czarna Białostocka is 9,596, that of Wasilków is 8,967, that of Choroszcz is 5,416, that of Supraśl is 4,578, that of Zabłudów is 2,400, that of Tykocin is 1,893, that of Suraż is 982, and the rural population is 86,382.