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 (software), an integrated online system for the management and processing of securities
- GEOS (software library), a free software topology library
- Other
- GEOS (eikaiwa), an English conversation teaching company 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-1, 2 (Geodetic Earth Orbiting Satellite), research satellites from NASA
- GEOS-3 (Geodynamics Experimental Ocean Satellite), a research satellite from NASA
- GEOS-1 (Goddard Earth Observing System version 1), Earth model from NASA EOS Program