GEOS may refer to:
Computer software GEOS (8-bit operating system), an operating system originally designed for the Commodore 64 GEOS (16-bit operating system), a DOS-based graphical user interface and x86 operating system GEOS (securities processing software), an integrated online system for the management and processing of securities GEOS (software library), an open-source geometry engine Goddard Earth Observing System, an Earth system model
Other GEOS (eikaiwa), a defunct operator of English conversation teaching schools based in Japan GEOS circle, an intersection of four lines that are associated with a generalized triangle GEOS (satellite), a research satellite from ESRO (1978–1982) GEOS (satellite series), three research satellites from NASA Groupe GEOS, a French business consultancy