Sumatra, Indonesia, has a long and checkered history of mineral exploration and mining that dates back to prehistoric times. These activities have been dominated by gold, involving both the local population and mostly foreign companies. The first documented mining activity was the reopening of the ancient silver-rich Salida gold mine in West Sumatra in 1669 by the VOC (Vereenigde Oost-Indische Compagnie), a Dutch trading company that for two centuries monopolized trade between Europe and Asia. The government of the Netherlands East Indies initiated geologic investigations and mineral exploration in 1850, and private industry followed 30 years later. Between 1899 and 1940, 14 gold mines were developed, most of which were short-lived and uneconomic. Total production between 1899 and 1940 was 101 t Au and 1.2 Mt Ag. During the Japanese occupation, in its aftermath, and for the first 20 years of Indonesia’s independence, there was very little activity. In 1967, introduction of new foreign investment and mining laws by the New Order government heralded a new era of exploration and mining activity that continues to the present day. Since 1967, there have been several peaks in exploration activity, viz. 1969 to 1973 (porphyry copper), 1985 to 1990 (gold), 1995 to 1999 (gold), and 2006 to 2010 (multi-commodity). A variety of previously unknown mineralization types were discovered, including porphyry Cu, high-sulfidation Au, sediment-hosted Au, and sediment-hosted Pb-Zn. Activity during the modern area has included the reopening of one of the old Dutch mines, development of four new gold discoveries including the giant Martabe district (310 t Au), and exploitation of several small Fe skarn deposits known from the Dutch time. By world standards, to this day Sumatra remains underexplored.