The aim of this article is to investigate Turkey's main energy sources and importance of its usage in the energy sector. Turkey is rapidly growing in terms of both its economy and population due to its demand for energy. Domestic coal, geothermal, and hydropower reserves of Turkey are approximately 1% of the world's total. In this respect, Turkey's domestic energy production has not exceeded 40% of its energy demand. For this reason, Turkey is a net energy importer and also the energy demand of Turkey is expected to be doubled between the years 2000 and 2010 and be fourfold between the years 2000 and 2025. Turkish energy policy is mainly concentrated on assurance of energy supply in a reliable manner and sufficiently in time, under economic and clean terms and in a way to support and orientate the target growth and social developments.