| Trustix | Comodo Group | — | GNU General Public License |
| TTOS Linux | — | — | — |
| Tucunaré | — | — | — |
| Tuga | — | — | GNU General Public License |
| Tukaani Linux | — | — | — |
| Turkix | — | — | — |
| TurnKey Linux Virtual Appliance Library | — | — | — |
| Tuxedo OS | — | — | — |
| Twister OS | — | — | freeware |
| U-Lite | — | — | GNU General Public License |
| UberStudent | — | — | GNU General Public License |
| Ubix Linux | — | — | — |
| Ubuntu | Canonical Ltd. | 2004 | — |
| Ubuntu Budgie | — | — | GNU General Public License |
| Ubuntu Christian Edition | User community | — | — |
| Ubuntu Cinnamon | — | — | — |
| Ubuntu Core | — | — | — |
| Ubuntu GNOME | Canonical Ltd. | 2016 | GNU General Public License |
| Ubuntu Kylin | National University of Defense Technology | — | GNU General Public License |
| Ubuntu MATE | — | — | GNU General Public License |
| Ubuntu Mobile | Canonical Ltd. | — | GNU General Public License |
| Ubuntu Netbook Edition | Canonical Ltd. | — | GNU General Public License |
| Ubuntu Privacy Remix | — | — | — |
| Ubuntu Satanic Edition | — | — | — |
| Ubuntu Server Edition | Canonical Ltd. | 2006 | GNU General Public License |
| Ubuntu Studio | Canonical Ltd., Ubuntu Foundation | 2007 | GNU General Public License |
| Ubuntu Sway Remix | — | — | — |
| Ubuntu Touch | UBports | 2013 | GNU General Public License |
| Ubuntu Unity | — | 2020 | — |
| Ubuntu Web | — | — | — |
| UbuntuDDE Remix | — | — | GNU General Public License, version 3.0 |
| UCS@school | Univention | — | GNU Affero General Public License |
| Ufficio Zero | — | 2020 | GNU General Public License |
| UKnow4Kids | — | — | GNU General Public License, version 2.0 |
| Ultima Linux | — | — | GNU General Public License |
| Ultimate Edition | — | — | — |
| Ultimate Linux | — | — | — |
| Ultramarine Linux | — | — | — |
| Umbrel OS | — | — | PolyForm Noncommercial License |
| Umbrella Linux | — | — | — |
| Unity Operating System | — | 2020 | — |
| Univention Corporate Server | — | — | GNU Affero General Public License |
| Uruk GNU/Linux | — | — | — |
| USU | — | — | GNU General Public License |
| Ututo | — | — | GNU General Public License |
| UwUntu | — | — | Creative Commons Attribution 4.0 International |
| Vanilla OS | — | — | GNU General Public License, version 3.0 |
| VectorLinux | — | — | — |