Jönköping County (Swedish: Jönköpings län) is a county or län in southern Sweden. It borders the counties of Halland, Västra Götaland, Östergötland, Kalmar and Kronoberg. The total county population was 356,291 inhabitants in September 2017. The capital and largest city is Jönköping. About one quarter of the total county population lives in the combined Jönköping-Huskvarna urban area around the southern point of Lake Vättern.

Despite being commonly used to indicate the geographical, cultural and historical region, the larger historical province (landskap) of Småland, which most of Jönköping County is part of, has no administrative or political significance today. Jönköping County has existed as an administrative division since the 17th century, and constitutes the north-western part of Småland, the other parts being Kronoberg County in the south-west and Kalmar County in the east. Jönköping County was periodically united with neighbouring Kronoberg County until 1687. Until the 18th century the administration was housed in the renaissance fortress at Jönköping Castle, which was demolished in the 19th century; the former site of the castle is still the site of the County Administrative Board building and the Governor's residence.

Habo Municipality and Mullsjö Municipality, from the south-eastern part of the historical province of Västergötland, are since the dissolution of Skaraborg County in 1998 also part of Jönköping County; both municipalities joined Jönköping County as the results of local referendums in 1997.

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