Kapteyn may refer to:
- Jacobus Kapteyn - Astronomer
- Parallactic instrument of Kapteyn - the instrument used by Kapteyn to analyze photographic plates
- Jacobus Kapteyn Telescope - telescope named after Jacobus Kapteyn
- Kapteyn's Star - star named after Jacobus Kapteyn
- Kapteyn (crater) - Lunar crater named after Jacobus Kapteyn
- Kapteyn Astronomical Institute - Dutch Astronomical Institute named after Jacobus Kapteyn
- Paul Joan George Kapteyn - Dutch Judge