Siemiatycze County (Polish: powiat siemiatycki) is a unit of territorial administration and local government (powiat) in Podlaskie Voivodeship, north-eastern Poland, on the border with Belarus.

It came into being on January 1, 1999, as a result of the Polish local government reforms passed in 1998.

Its administrative seat and largest town is Siemiatycze, which lies 80 kilometres (50 mi) south of the regional capital Białystok.

The only other town in the county is Drohiczyn, lying 15 km (9 mi) west of Siemiatycze.

The county covers an area of 1,459.58 square kilometres (563.5 sq mi).