Developments in the fundamental optics for soft X-ray interferometry and holography are reviewed. To improve the quality of interference fringes it is essential to develop the soft X-ray sources, optical components and recording films. In this study soft X-ray radiation emitted from the undulator arranged in the 2.5 GeV Photon Factory ring was used, as well as radiation from the microfocus X-ray Generator. The coherence properties of undulator radiation were examined by the interference technique. Owing to the recent development of microfabrication technology, soft X-ray optical components such as Fresnel zone plates, transmission gratings, grazing incidence mirrors and multilayers are available for collimating, focussing, splitting or monochromatizing soft X-ray radiation. These components provides various possibilities for the optical system of interferometric and holographic experiments. As recording films, PMMA and inorganic resists with a high spatial resolution, as well as conventional films, are useful. The interferometric and holographic patterns were recorded by adopting several fundamental optical geometries such as the Lloyd's mirror arrangement, the Gabor in-line geometry and the Fourier transform geometry. The holograms with fringes several hundred Ångstrom wide were observed. Finally the prospects for further development are discussed.