Koszalin (German: Köslin; Kashubian: Kòszalëno; Latin: Cussalin) is the largest city of Middle Pomerania in north-western Poland. It is located 15 km south of the Baltic Sea coast. Koszalin is also a county-status city and capital of Koszalin County of West Pomeranian Voivodeship since 1999. Previously, it was a capital of Koszalin Voivodeship (1950-1998).

In 1214 Bogislaw II, duke of Pomerania made a donation of a village known as Koszalice/Cossalitz by Chelmska Hill in Kolobrzeg Land (una villa ... Cussalitz iuxta Cholin in terra Cholbergensis) to the Premonstratensian (Norbertine) monastery in Bialoboki (Belbuck) near Trzebiatów (Treptow an der Rega). New, mostly German, settlers from outside of Pomerania were invited to settle the territory. In 1248 the eastern part of Kolobrzeg Land, including the village, was transferred by Duke Barnim I to the Roman Catholic Diocese of Kammin.[1] On 23 May 1266, Kammin bishop Hermann von Gleichen granted a charter to the village Cussalin, giving it Lübeck law, local government, autonomy and multiple privileges; it became known in German as Cöslin. When in 1276 the bishops became the sovereign in neighboring Kolobrzeg, they moved their residence there, while the administration of the diocese was done from Koszalin.[1] The city obtained direct access to the Baltic Sea when it gained the village of Jamno (1331), parts of Lake Jamno (Jamunder See, now Jezioro Jamno), a spit between the lake and the sea and the castle of Nest (now Uniescie) (1353). Thence, Cöslin participated in the Baltic Sea trade as a member of the Hanseatic League, which led to several conflicts with the competing seaports of Kolberg (Kolobrzeg) and Rügenwalde (Darlowo). From 1356 until 1417/1422, the city was part of the Duchy of Pomerania-Wolgast.