Kara-Su (meaning "Black Water") is a valley in southwestern Kyrgyzstan, contained within the Pamir range.

The Kara-Su is home to two towns; one at N 40.71 E 72.89, the other, known as Kaindy-Kara-Su , at N 51.48 E 64.40

"Kara-Su" is also the name of a river in Bulgaria, also called the Struma River, that flows into the Aegean Sea.