Over the past several decades, inorganic membranes composed of zeolite, silica, carbon, and metal/organic frameworks (MOF) have improved dramatically in terms of fabrication and application. Pure silica (SiO2) and organosilica membranes for use in molecular separation are the focus of this review. First, the fabrication of these silica-based membranes is outlined to highlight the great progress achieved in sol-gel and CVD processing. Then, applications in gas- and liquid-phase separations and an evaluation of pore sizes are summarized and future perspectives are discussed.