Castres is a city located in southern France within the Occitanie region. It serves as the sole subprefecture of the Tarn department and is situated in the area formerly known as the province of Languedoc.
As of 2023, the commune has a population of 42,505. While it lies within the former province of Languedoc, it is not part of the former region of Languedoc-Roussillon.