| Familiar Linux | — | — | GNU General Public License |
| Fantoo | — | — | — |
| Feather Linux | — | — | — |
| Fedora AOS | — | — | — |
| Fedora CoreOS | — | — | — |
| Fedora Legacy | — | — | — |
| Fedora Linux | Red Hat, IBM, Fedora Project | 2003 | MIT License |
| Femto OS | — | — | GNU General Public License |
| Feren OS | — | — | — |
| Fermi Linux | Fermilab | — | GNU General Public License |
| Finnix | Ryan Finnie | — | — |
| Fira OS | — | — | — |
| Fire OS | Amazon | 2011 | GNU General Public License, Apache License |
| FireballISO | Indy | — | — |
| Firefox OS | Mozilla Foundation, Mozilla Corporation | — | Mozilla Public License, Apache License, free license |
| Fiwix | — | — | — |
| Flame-Sim | — | — | — |
| FLEX | Technical Systems Consultants | — | — |
| FlexOS | Digital Research | — | — |
| Fli4l | — | — | GNU General Public License |
| Floppyfw | — | — | — |
| Fluxbuntu | — | — | GNU General Public License |
| Flyme | Meizu | — | GNU General Public License, Apache License |
| FMI/OS | — | — | GNU General Public License |
| Foresight Linux | — | — | GNU General Public License |
| FortiOS | Fortinet | — | — |
| Fox Linux | — | — | — |
| FreeBSD | — | 1993 | 2-clause BSD License |
| FreedomBox | — | — | GNU Affero General Public License, version 3.0 or later |
| FreeDOS | Jim Hall | 1998 | GNU General Public License |
| FreeDOS-32 | — | — | GNU General Public License, version 3.0 |
| Freedows OS | — | — | — |
| Freeduc-cd | UNESCO | — | — |
| FreeNOS | — | — | GNU General Public License, version 3.0 |
| FreeRTOS | — | 2003 | MIT License |
| FreeSBIE | — | — | BSD licenses |
| FREESCO | — | — | GNU General Public License, version 2.0 |
| Freespire | Linspire | — | GNU General Public License, proprietary license |
| Freetz | Eugen Rudoy | — | GNU General Public License, version 2.0 |
| FreeVMS | — | — | GNU General Public License, version 3.0 |
| FreeWRT | — | — | GNU General Public License |
| Frenzy BSD | — | — | BSD licenses |
| Frugalware Linux | Miklós Vajna | — | GNU General Public License |
| Fuchsia | Google | — | Apache License, MIT License, 3-clause BSD License |
| Fuduntu | — | — | GNU General Public License |
| FuguIta | — | — | — |
| Fully Automated Nagios | — | — | — |
| Funtoo Linux | Daniel Robbins | — | — |
| Funtouch OS | Vivo | — | — |
| FuryBSD | — | 2019 | BSD licenses |
| Fusion Linux | — | — | — |
| FUSS | — | — | GNU General Public License |
| Fuzix OS | Alan Cox | — | GNU General Public License, version 2.0 |
| FydeOS | — | — | — |