Dalarna County (Dalarnas län) is a county or län in middle Sweden. It borders the counties of Jämtland, Gävleborg, Västmanland, Örebro and Värmland. It is also bordered by the Norwegian counties of Hedmark and Sør-Trøndelag in the west. The capital is Falun.

The term Dalarna County is mainly used for administrative purposes, being further subdivided into municipalities (kommuner). Dalarna County virtually encompasses the historical province Dalarna (literally, "the valleys"), that deals with history and culture of the area.

In older times, Dalarna was periodically part of the territory ruled by the governor of Västerås Castle. The 1634 Instrument of Government led to the creation of a county covering Dalarna with its own County Governor. The Kopparbergs län (literally Copper Mountain County) was finally created by royal decree in 1647. In 1997, the name of the county was changed to Dalarna County.

The main aim of the County Administrative Board is to fulfil the goals set in national politics by the Parliament and the Government, to coordinate the interests and promote the development of the county, to establish regional goals and safeguard the due process of law in the handling of each case. The County Administrative Board is a Government Agency headed by a Governor. See List of Dalarna Governors.

 Dalarna (help·info), English exonym: Dalecarlia, is a historical province or landskap in central Sweden. Another English language form established in literature is the Dales. Places involving the element Dalecarlia exist in the United States.

Dalarna adjoins Härjedalen, Hälsingland, Gästrikland, Västmanland and Värmland. It is also bounded by Norway in the west.

The word "Dalarna" means "the dales" (valleys). The area is a popular vacation destination for Swedes from the south, who often travel there to relax during summer vacations, drawn by good fishing lakes, beautiful campgrounds, and deep forests. Many such Swedes own or rent a second residence in Dalarna, where they are likely to have a vegetable garden and apple trees. In mid-June, summerfest celebrations and dances are held in many of the small villages and, of course, in the larger cities. Dalarna is a region full of historical associations, possessing strong local characteristics in respect of its products, and especially of its people. In the western districts of Älvdalen and Lima some people in villages speak a traditional dialect, the Dalecarlian language. Historically, the people of Dalecarlia - called Dalecarlians, or Dalesmen (dalkarlar, dalmasar) and Daleswomen (dalkullor) - are famous for their love of independence.