Nowy Tomyśl County (Polish: powiat nowotomyski) is a unit of territorial administration and local government (powiat) in Greater Poland Voivodeship, west-central Poland.

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 Nowy Tomyśl, which lies 55 kilometres (34 mi) west of the regional capital Poznań.

The county contains three other towns: Opalenica, 20 km (12 mi) east of Nowy Tomyśl, Zbąszyń, 17 km (11 mi) south-west of Nowy Tomyśl, and Lwówek, 16 km (10 mi) north of Nowy Tomyśl.

The county covers an area of 1,011.67 square kilometres (390.6 sq mi).