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.