This chapter deals with purely organic superconductors. Materials of this kind have attracted much attention from the viewpoint of not only scientific interest but also practical applications in organic electronic devices. The chapter reviews the several kinds of purely organic superconductors as well as the efforts on for the development of related materials. It is well known that common organic materials are insulating. The highest occupied molecular orbital of a closed-shell molecule is fully occupied. The development of single-component molecular metals and superconductors using closed-shell organic compounds has been also reported. The chapter describes several molecules as candidates for superconductors composed of organic molecules in terms of a chemical approach. These results indicate that metallic conductivity and superconductivity are hardly realized under ambient conditions. Observed uniform molecular arrangements and three-dimensional heteroatom networks are advantageous to high conductivity under pressure.