Dalarna County (Swedish: Dalarnas län) is a county or län in central Sweden (Svealand). It borders on the counties of Uppsala, Jämtland, Gävleborg, Västmanland, Örebro and Värmland. It also borders on the Norwegian counties of Hedmark and Trøndelag to the west. It was formerly known as Kopparberg County (Swedish: Kopparbergs län) until the name was changed to that of the provincial region on 1 January 1997. The province of Dalarna is slightly larger than the county, as the westernmost part of Ljusdal Municipality belongs to it.
The term Dalarna County is mainly used for administrative purposes; it is further divided into municipalities (kommuner). Dalarna County encompasses nearly all of the cultural and historical province of Dalarna (literally, "the valleys"). For the most part sparsely populated and with extensive tracts of wilderness, Dalarna County is almost as large as Belgium in terms of land area.