Sibolga is a city and a port on the west coast of North Sumatra province in Indonesia. It is located on the western side of North Sumatra, facing the Indian Ocean and is a transit harbor to Nias island. Sibolga has beaches and coral gardens in a sea dotted with islands, but was hard hit during the 2004 Indian Ocean Earthquake.
Poncan Ketek Island (Small Poncan Island) in Sibolga Bay was once the location of a fort. British, Dutch, French and American traders passed through here. Ferries from Sibolga service the outlying islands to the west, Simeulue and Nias, as well as the rest of Indonesia.
It is the site of the Sibolga Open Water Swimming Competition, a 10 km open water swim.