Lake Toba (Malay: Danau Toba) is a large crater lake in the province of North Sumatra in Sumatra, in Indonesia. It originated as a caldera from a huge volcanic eruption (a super volcano) some 70-75,000 years ago; see Toba.

Lake Toba has a peninsula that was created about 30,000 years ago as a result of a volcanic eruption. This island, called Samosir, measures approximately 46 km by 21 km and is a popular destination especially for backpackers. It is inhabited by the Toba Batak. On the island are some villages with Batak houses, such as Ambarita, Tomok and Simanindo. In Huta Bolon, residents perform daily dance performances.

Lake Toba, especially the town of Prapat, is a popular holiday destination for people from Medan. The temperature (about 27 ° C during the day and about 22 ° C in the evening) is low by Indonesian standards, and is pleasantly cool compared to the tropical heat of Medan with about 31 ° C.