The counties of Sweden (Swedish: Sveriges län) are the first-level administrative subdivisions of Sweden. There are twenty-one counties; however, the number of counties has varied over time, due to territorial changes and to divisions or mergers of existing counties.

This level of administrative unit was first established in the 1634 Instrument of Government on Lord Chancellor Count Axel Oxenstierna's initiative, and superseded the landskap, in order to introduce a more efficient administration of the realm. The county borders often follow the provincial borders, but the Crown often chose to make slight relocations to suit its purposes.

In every county there is a county administrative board (länsstyrelse) headed by a governor (landshövding), appointed by the government, as well as a separate regional council (region). In the county of Gotland however, the county's only municipality has adopted regional responsibilities. The aims of the county administrative board are to supervise local state administration (that is not otherwise assigned to other government agencies), and to coordinate political goals with the central government. The regional council is the elected regional political assembly that oversees the municipal affairs of the county, primarily in regard to public healthcare, public transport, and culture.

Beginning in the 2000s, many major government agencies have reorganised from a county-based subdivisional structure into larger geographical or functional areas. This include the Swedish Tax Agency (1 January 2004), the Swedish Social Insurance Agency (1 January 2005), the Swedish Public Employment Service (1 January 2008), and the Swedish Police Authority (1 January 2015).

With county codes, which were official until 1974.

Each county region contains a number of municipalities (kommuner), the existence of which is partly at the discretion of the central government. Since 2004 their number has been 290, thus an average of 13.8 municipalities per county.

Until 1968, the City of Stockholm had its own "county code" A, which is still used interchangeably with AB in some contexts, and County of Stockholm had county code B. L was for Kristianstad County and M was for Malmöhus County but since they were merged to form Skåne County, M is usually used. O used to stand for Gothenburg and Bohus County but has been used for Västra Götaland County since it was merged with Skaraborg County (R) and Älvsborg County (P).

Sweden's provinces, or landskap, and the "lands", or landsdelar, lack political importance today but are common denominations culturally and historically. The provinces had their own laws and justice systems and could have large cultural and religious differences. The province of Småland (literally small land) historically was several provinces with its own laws. Here burial tradition in the era before the Viking Age could differ significantly from province to province. The province of Norrbotten is a relatively recent creation; it was part of Västerbotten which extended all the way to Österbotten in today's Finland before 1809. Finnish and Swedish Lapland formed a single province until 1809.