Una Una (also known as Colo) is an isolated volcano in the Gulf of Tomni, offshore central Sulawesi. It is the site of sulfur extraction.

Una Una volcano is a broad, low volcano containing a 2-km-wide caldera with a small central cone. Only 3 eruptions are known in historic time, but 2 of them caused extensive damage over much of the island. The last eruption of Una Una was in 1983 and produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.