Karlshamn is a locality and the seat of Karlshamn Municipality in Blekinge County, Sweden. Karlshamn received a Royal Charter and city privileges in 1664, when King Charles X Gustav, in Swedish Karl, realized the strategic location near the Baltic Sea. In 1666 the town was named Karlshamn, meaning Karl's Port in honour of the Swedish king. At the outlet of the stream Mieån was found a harbour and fishing village "Bodekull" and a farm "Bodetorp". In the lower parts of "Mörrumsån" was a prosperous salmon fishery.
Sweden gained supremacy over the territory through Treaty of Roskilde 1658. The king Charles X Gustav immediately inspected the coast and found here a tremendously beautiful and incomparable harbour. Fortifications designed by Erik Dahlberg were erected on Boön 1659 and on Friesholmen 1675, called "Kastellet". Troops loyal to the Danish king attacked the town twice in 1676-78. The location attracted foreign merchants and in 1664 royal privileges were issued to establish a town named after the king, meaning "Karl's Port". The settlement expanded rapidly to count 647 citizens in the year 1700. Pestilence reduced the population in 1710.
Industries based on agricultural and mineral products were established during the 18th century. A fire 1763 destroyed the northern part of the town, another fire ravaged in 1790. The intercontinental war of 1810 gave Karlshamn a rare possibility to trade goods and the citizens prospered. Punch, tobacco and snuff powder were produced in town. Craftmanship was common until circa 1880, when industrial production took over. The town had 6529 citizens 1883, the town plan covered 63 hectares and on 693 plots were buildings erected. The railway inaugurated 1874 connected Karlshamn to Vislanda in the northern province. 1890 the coastal railroad was built. 1876 L.O. Smith established production of aquavit in the town and built a new distillery in 1884 which was effective until 1893, whereafter it was converted to a sugar refinery. In 1912 was established production of vegetable oil in the old refinery, a still continuing operation under the label AAK. Stone cutting in granite quarries was a heavy export industry circa 1850–1940. In Mörrum a paper mill was built in 1962. The port of Karlshamn has gradually since 1975 transferred its operations to the Stilleryd location west of town.
The earlier spelling was CARLSHAMN.