Abstract This article describes glass fibers derived from silica, alumina, and calcium oxide compositions. The section on general-purpose glass fibers provides an in-depth discussion of melt properties, fiber properties, methods of manufacture, and significant product types. The article discusses special-purpose glass fibers and reviews compositions, manufacture, properties, and applications to an extent commensurate with their commercial use. It addresses the generic glass melting and fiber forming process, including the viscosity-versus-temperature profile required for general-purpose E-glass fibers with and without boron. The article also discusses continuous multiend or single-end roving, woven roving (or noncrimp fabrics), fiberglass mats, chopped strands, and yarns for textile applications.