Colo, Stratovolcano in Una-Una Island, Sulawesi, Indonesia.

Colo is a stratovolcano on Una-Una Island in the Gulf of Tomini, rising roughly 500 meters above sea level. The mountain features a wide crater with a smaller volcanic cone inside, and forms the entirety of the island itself.

Three eruptions of Colo are documented. In 1898 residents were evacuated before an eruption that caused only material damage. From 9 July 1983 volcanic earthquakes preceded the first eruption on 19 July; pyroclastic flows on 21 July devastated about 80% of Una Una, and ash reached Sulawesi. A British Airways flight to Perth entered the ash cloud on 23 July and turned back to Singapore. Explosions continued until 26 August 1983.

The island's name, Una-Una, is commonly linked to the Indonesian word una, meaning 'coral', though the sources do not confirm this origin. After the 1983 eruption the population was resettled, and the volcano has stayed quiet since the last explosions of 26 August 1983. In mid-August 1983 the French volcanologists Katia and Maurice Krafft visited the island and documented the damage.

Reaching the island requires authorization from local authorities and it is wise to check current volcanic activity before visiting. Visitors should gather local information on-site since conditions can vary depending on weather and volcanic activity.

The 1983 eruption buried about 80% of Una Una in pyroclastic flows, and on 23 July a British Airways flight bound for Perth flew into the ash cloud and turned back to Singapore. Volcanologists Katia and Maurice Krafft reached the island by mid-August 1983 to document the damage.