Jämtland County (Swedish: Jämtlands län, Southern Sami: Jiemthen leene) is a county or län in Sweden. It consists of the provinces of Jämtland and Härjedalen, along with minor parts of Hälsingland and Ångermanland, plus two small strips of Lapland and Dalarna. It borders the counties of Dalarna, Gävleborg, Västernorrland, and Västerbotten, as well as the Norwegian county of Trøndelag. It measures 49,443 km2 (19,090 sq mi) and constitutes 12% of Sweden's total area, making it the country's third largest county. The capital is Östersund. The county governor and leader of the administrative board, as appointed by the Swedish government, has been Marita Ljung since 2021.
The county was established in 1810, at which time it consisted only of the provinces of Jämtland and Härjedalen, which is why the coat of arms is a shield parted per fess with their provincial arms. His Majesty King Carl XVI Gustaf is occasionally referred to as Duke of Jämtland after his title of king.