Qara Su, Qarasu or Los Island, is an uninhabited sandy island off the Bay of Baku, Azerbaijan. This island is part of the Baku Archipelago, which consists of the following islands: Boyuk Zira or Nargin, Dash Zira, Kichik Zira (Qum or Sandy Island), Zenbil, Sangi-Mugan, Chikil, Qara Su, Khara Zira, Gil, Ignat Dash and a few smaller ones.
Qara Su is an island of tectonic origin. It has a length of 900 m, and a width of 600 m. Formerly there were large gas fields on the island. Qara Su's surrounding waters are very shallow. There is very little vegetation on the island due to oil pollution as well as other factors.
Caspian seals, sturgeon, and numerous types of birds, like teal ducks, herring gulls, and grebes are some of the species that can be found on and around Qara Su Island.