Oil shales, which are kerogen-rich sediments, are one of the most important energy alternatives. The widely distributed deposits around the world and their vast amounts make them a promising option as a source of oil or as a solid fuel supplement. Nevertheless, the economics of retorting does not allow their utilization for oil production on a large scale with a few exceptions. Oil shale is an important potential energy resource for Turkey, being the second largest fossil energy source after lignite. This paper aims to emphasize the important aspects about oil shales so as to give ideas about their importance as an alternative source. The definition of oil shale, mode of occurrence and the use of resources in the world and in Turkey are reviewed and the opportunities for prospective utilization in the future are provided.