| Koski Tl | |
| Official Name: | Finnish: Kosken Tl kunta Swedish: Koskis kommun |
| Other Name: | Koskis |
| Settlement Type: | Municipality |
| Coordinates: | 60.655°N 31.5°W |
| Subdivision Type: | Country |
| Subdivision Name: |  Finland |
| Subdivision Type1: | Region |
| Subdivision Name1: | Southwest Finland |
| Subdivision Type2: | Sub-region |
| Subdivision Name2: | Loimaa sub-region |
| Leader Title: | Municipal manager |
| Leader Name: | Aimo Suikkanen |
| Established Title: | Charter |
| Established Date: | 1869 |
| Blank3 Name: | Climate |
| Blank3 Info: | Dfc |
| Timezone: | EET |
| Utc Offset: | +02:00 |
| Timezone Dst: | EEST |
| Utc Offset Dst: | +03:00 |
Koski Tl (pronounced as /fi/; sv|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 and covers an area of NaNKoski Tl}} of which NaNKoski Tl}} is water. The population density is NaNKoski Tl.
Tl in the name means the former province of Turku and Pori (fi|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, fi|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.
Hämeen Härkätie runs through Koski and it crosses the Paimio River in the center of Koski. The church of Koski was designed by architect Toivo Paatela and it was completed in 1935. There is also an observation tower near the highest points of Hevonlinna ridge and Hevonlinnanjärvi.
Yrjö Liipola Art Museum is exhibiting Yrjö Liipola's art collection.