Koski Tl (Finnish pronunciation: [ˈkoski]; Swedish: Koskis) is a municipality of Finland.
It is located in the Southwest Finland region and was part of the former province of Western Finland. The municipality has a population of 2,194 (31 August 2024) and covers an area of 192.42 square kilometres (74.29 sq mi) of which 0.96 km2 (0.37 sq mi) is water. The population density is 11.46 inhabitants per square kilometre (29.7/sq mi).
Tl in the name means the former province of Turku and Pori (Finnish: Turun ja Porin lääni). It was attached to the name to distinguish Koski Tl from another municipality named Koski, Koski Hl (Hl for the former province of Häme, Finnish: Hämeen lääni). Koski Hl was renamed Hämeenkoski in 1995 but Koski Tl has not changed its name.
Koski is unilingually Finnish.
Koski's neighbouring municipalities are Loimaa, Marttila, Pöytyä, Salo, Somero and Ypäjä.
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