| Galileo | Acorn Computers | — | — |
| Galinux | — | — | — |
| GalliumOS | — | — | — |
| Galsoft Linux | — | — | GNU General Public License |
| Gargoyle | — | — | GNU General Public License, version 2.0 |
| Garuda OS | — | 2020 | — |
| GeckoLinux | — | 2016 | — |
| GeckOS | — | — | GNU General Public License |
| GeeXboX | — | — | GNU General Public License |
| GendBuntu | National Gendarmerie | — | — |
| Genera | Symbolics | — | — |
| General Comprehensive Operating System | General Electric | 1962 | proprietary license |
| Gentoo GNU/Hurd | — | 2026 | GNU General Public License, version 2.0 |
| Gentoo Linux | — | — | GNU General Public License |
| Gentoo/Alt | — | — | — |
| Gentoo/FreeBSD | — | — | — |
| Gentoox | — | — | — |
| GENtOS | — | — | — |
| GEORGE | International Computers and Tabulators | — | — |
| GEOS | GeoWorks | 1990 | Apache License |
| GEOS | GeoWorks | 1986 | proprietary license |
| Geubuntu | — | — | — |
| Ghost | — | — | GNU General Public License, version 3.0 |
| GhostBSD | — | 2009 | GNU General Public License, 2-clause BSD License |
| Glass OS | Google | — | — |
| Glaze OS | — | 2017 | — |
| GLinux | — | — | — |
| GlobalView | Xerox | 1986 | — |
| GM-NAA I/O | General Motors Research Laboratories, North American Aviation | — | — |
| GMOS | General Motors | — | — |
| GNewSense | — | — | GNU General Public License |
| GNIX | — | — | — |
| GNO/ME | — | — | — |
| GNOME OS | — | — | — |
| Gnoppix | — | — | GNU General Public License |
| GNOSIS | Tymshare | — | — |
| GNU | GNU Project | — | GNU Lesser General Public License, GNU General Public License, GNU Affero General Public License |
| GNU Anastasis | — | — | GNU Affero General Public License, version 3.0 or later, GNU General Public License v3.0 or later |
| GNU Guix System | GNU Project | — | free software license |
| GNU/Hurd | — | — | — |
| GNU/Linux | Richard Stallman, Linus Torvalds | — | GNU General Public License |
| GnuLinEx | — | — | GNU General Public License |
| GnYOUlinux | — | — | — |
| GobMis GNU/Linux | — | — | — |
| GoboLinux | — | — | GNU General Public License |
| Gobuntu | Canonical Ltd. | 2007 | GNU General Public License |
| Goobuntu | — | — | — |
| Google TV | Google | 2010 | — |
| Googlebook OS | Google DeepMind, Google | — | — |
| GOS | — | — | Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported |
| GP32 System Software | — | — | — |
| GParted Live | — | — | — |
| Granular Linux | — | — | — |
| GrapheneOS | Daniel Micay | 2016 | MIT License, GNU General Public License, version 2.0 |
| Greenbone OS | Greenbone AG | — | — |
| Grml | — | — | — |
| Group Control System | IBM | — | — |
| Guadalinex | Government of Andalusia | — | GNU General Public License |