- Kaas by Carson City (19 features)
- Kachan by nonniemas (64 features)
- Kagian by Peter Cannici (84 features)
- Kaidu by Kyle Farrington (90 features)
- Kaingu by Brv (127 features)
- Kaitiri by Original Queen Xalele (8 features)
- Käläli by Serali (9 features)
- Kalasic by Stephen T. (3 features)
- Kalavi by kalathei95 (145 features)
- Kali-Sise by Jeffrey Henning (110 features)
- Kamakawi by David J. Peterson (141 features)
- Kamëzet by loglorn (132 features)
- Kanabi by couldntremembermypassword (1 feature)
- Kangir by Appleseed (139 features)
- Kannow by Nortaneous (64 features)
- Kanteian by Finlay (17 features)
- Karemar by O. Duke (46 features)
- Kashithes by Bookhobbit (32 features)
- Kassunetian by Taylor Selseth (143 features)
- Kata by Katapraktoi (34 features)
- Katkagor by C.M.Torrens (58 features)
- Kaujasakka by Fu Lei (141 features)
- Kavrinian by Ultimate Ridley, k1234567890y (143 features)
- Kaynuryos by Pirka (123 features)
- Kayronic by Hendrie Corbie (84 features)
- Kazujisha by Avaja (101 features)
- Kedshi by total (145 features)
- Keeltyewarem by Dillon Hartwig (0 features)
- Keihansoukaishi by Akira Tsuchiya (?) (87 features)
- Keintra by Peter Himin (4 features)
- Kelanian by Andre (124 features)
- Kēlen by Sylvia Sotomayor (60 features)
- Kelenala by David J. Peterson (141 features)
- Keltsvian by Republicanspaniard (85 features)
- Kemba by David Johnson (124 features)
- Kesh by Rebecca Ashling (13 features)
- Keylim by arimaz (13 features)
- Khafos by Josh Regev (94 features)
- Khanese by Andres R (54 features)
- Khangathyagon by Pete Bleackley (120 features)
- Khan Nilau Khaftim by Becca (125 features)
- Khengjûl by Tapeworm (7 features)
- Khulls by Soap (47 features)
- Khuzdul by Aulë (in-fiction), J. R. R. Tolkien(out-of-fiction) (8 features)
- Kiassan Turasta by Kári Emil Helgason (119 features)
- Kibaki by ttaga (36 features)
- Kiitra by D. R. Merrill (145 features)
- Kipusan by Blissom (60 features)
- Kiriyow (Creole) by Kiriyow (73 features)
- Kirronga by Chagen (132 features)
- Kisimbi by Josef Wolanczyk (Quetanto) (59 features)
- Kisuna by Herman Miller (22 features)
- Kiswona by Benjamin Smith (140 features)
- Klik-Ma by Makeatah' (4 features)
- Klingon by Marc Okrand (143 features)
- Knashta by Ian Duncan (26 features)
- Koang by Naw Awng (4 features)
- Kobardon by Creyeditor (60 features)
- Kobold by Enrique Gamez (85 features)
- kolesch Speech by k1234567890y (119 features)
- Kolyma Ainu by protondonor (102 features)
- Konishien by arimaz (17 features)
- Kono Mai by phaed (103 features)
- Kopfberger German by k1234567890y (102 features)
- Korpasian by Taylor Selseth (141 features)
- Kostakan by PersonalJesus (22 features)
- Kotanian by Kilian Hekhuis (0 features)
- Kotava by collective under the pseudonym of Staren Fetcey (136 features)
- Kratish by Lars Klaenhammer (28 features)
- Krig by Jeff Sheets (74 features)
- Ksaedric by David Versaccio (0 features)
- Kti by Johannes Drucker (55 features)
- K'tle by Jeffrey S. Jones (120 features)
- K'u1k'uts' by Creyeditor (42 features)
- Kumiko by Ming (45 features)
- Kuty by cromulant (142 features)
- Kuyʔūn by Jan Strasser (117 features)
- Kymna by Roman Rausch (52 features)
- Kyuren by litrobotix (29 features)