| Jlime | — | — | GNU General Public License |
| JNode | — | — | GNU Lesser General Public License |
| Joatha Linux | — | — | — |
| Joli OS | — | 2011 | GNU General Public License |
| Jolicloud | — | — | proprietary license |
| Junos | Juniper Networks | — | — |
| Jurix | — | — | GNU General Public License |
| JUX | — | — | — |
| JX | University of Erlangen–Nuremberg | — | GNU General Public License |
| K42 | IBM | — | — |
| KaeilOS | KOAN | — | — |
| Kaella | — | — | — |
| KahelOS | — | — | — |
| KaiOS | KaiOS Technologies, Inc. | — | GNU General Public License, version 2.0 |
| Kaisen Linux | — | — | — |
| Kalango Linux | — | — | — |
| Kaleidoscope | — | — | — |
| Kali Linux | OffSec | 2013 | GNU General Public License |
| Kali Linux for Raspberry PI | — | — | — |
| Kali Purple | OffSec | — | GNU General Public License |
| KallistiOS | — | — | 3-clause BSD License |
| Kanotix | — | — | — |
| KaOS | — | 2013 | GNU General Public License |
| Kaspersky OS | Kaspersky Lab | — | — |
| KDE Linux | KDE | — | — |
| KDE neon | KDE | 2016 | GNU General Public License |
| Kdmix | — | — | — |
| KERNAL | Commodore International | — | — |
| KeshOS | — | — | — |
| Kid operating system | Thomas Petazzoni | — | — |
| KISS Linux | — | — | — |
| Kiwi Linux | — | — | — |
| KMON | — | — | — |
| KnightOS | — | — | MIT License |
| Knopperdisk | — | — | — |
| Knoppix | Klaus Knopper | — | GNU General Public License |
| Knoppix STD | — | — | — |
| KnoppMyth | — | — | — |
| KOBRA | Technische Universität Ilmenau, VEB Robotron | — | — |
| KolibriOS | — | — | GNU General Public License, version 2.0 |
| Kongoni GNU/Linux | — | — | — |
| Korora | — | 2016 | GNU General Public License |
| KSI Linux | — | — | — |
| Kubuntu | Canonical Ltd. | 2005 | GNU General Public License |
| Kuki Linux | — | — | — |
| Kurumin | Carlos Morimoto | — | GNU General Public License |
| Kwort Linux | — | — | — |
| Kylin | National University of Defense Technology | — | GNU General Public License |