| okgKoko Babangk | okg | Australian Aboriginal languages | | | 10 · Extinct |
| kznKokola | kzn | Niger–Congo | | | 6a · Vigorous |
| kkkKokota | kkk | Austronesian | | 530 | 6b · Threatened |
| biwKol | biw | Niger–Congo | | | 6a · Vigorous |
| kolKol | kol | — | | | 5 · Developing |
| eklKol | ekl | Austroasiatic | | | 6a · Vigorous |
| kvvKolabahasa Kola | kvv | Austronesian | | 500 | 6a · Vigorous |
| kfbKolava | kfb | Dravidian | | | 5 · Developing |
| klcKolbila | klc | Niger–Congo | | | 5 · Developing |
| sknKolibugan Subanen | skn | Austronesian | | | 6a · Vigorous |
| kshKölsch | ksh | Indo-European | | | |
| kmmKom | kmm | Sino-Tibetan | | | 5 · Developing |
| bkmKom | bkm | Niger–Congo | | | 3 · Wider Communication |
| kmyKoma | kmy | Niger–Congo | | | 6a · Vigorous |
| kpfKomba | kpf | — | | | 5 · Developing |
| tynKombaibahasa Kombai | tyn | — | | | 6b · Threatened |
| nuiKombe | nui | Niger–Congo | | | 6a · Vigorous |
| xbiKombio | xbi | Torricelli | | | 7 · Shifting |
| kgeKomeringCawa Kumoring | kge | Austronesian | | 470,000 | 6a · Vigorous |
| komKomiКоми кыв | kom | Uralic | | 219,100 | Definitely endangered |
| koiKomi-Permyakкоми-пермяцкӧй кыв | koi | Uralic | | 63,100 | 6b · Threatened |
| kpvKomi-ZyrianКоми кыв | kpv | Uralic | | 156,000 | 6b · Threatened |
| xoiKominimung | xoi | Ramu–Lower Sepik | | | 6b · Threatened |
| xomKomo | xom | Nilo-Saharan | | 18,530 | 6a · Vigorous |
| kmwKomo | kmw | Niger–Congo | | | 6b · Threatened |
| kvhKomodobahasa Komodo | kvh | Austronesian | | | 6b · Threatened |
| kvpKompane | kvp | Austronesian | | | 6b · Threatened |
| kzvKomyandaretbahasa Komyandaret | kzv | Trans–New Guinea | | | 6b · Threatened |
| kxwKonai | kxw | East Strickland | | | 5 · Developing |
| kndKondabahasa Konda | knd | — | | | 6b · Threatened |
| kfcKonda | kfc | — | | 20,000 | 5 · Developing |
| gauKondekor | gau | — | | | 5 · Developing |
| kdwKonerawbahasa Koneraw | kdw | Trans–New Guinea | | | 7 · Shifting |
| konKongokikongo | kon | Niger–Congo | | 5 m | Safe |
| kooKonjo | koo | Niger–Congo | | 609,000 | 5 · Developing |
| kokKonkani | kok | — | | 2.3 m | |
| xonKonkomba | xon | Niger–Congo | | | 5 · Developing |
| mjdKonkow | mjd | Maiduan | | | 9 · Dormant |
| kmaKonni | kma | Niger–Congo | | | 5 · Developing |
| knuKono | knu | Niger–Congo | | | 6a · Vigorous |
| knoKono | kno | Niger–Congo | | | 5 · Developing |
| klkKono | klk | Niger–Congo | | | 6a · Vigorous |
| koaKonomala | koa | Austronesian | | | 6b · Threatened |
| kczKonongo | kcz | Niger–Congo | | 51,000 | 6b · Threatened |
| kxcKonso | kxc | Afroasiatic | | 240,000 | 4 · Educational |
| nbeKonyak | nbe | Sino-Tibetan | | | 4 · Educational |
| kqyKoore | kqy | Afroasiatic | | 159,200 | 4 · Educational |
| xopKopar | xop | Ramu–Lower Sepik | | | 6a · Vigorous |
| opkKopkabahasa Kopka | opk | Trans–New Guinea | | | 6b · Threatened |
| kszKoraku | ksz | Austroasiatic | | | 6b · Threatened |
| kqzKorana | kqz | Khoisan | | | 9 · Dormant |
| kcyKorandje | kcy | Nilo-Saharan | | | 7 · Shifting |
| korKorean한국어 | kor | Koreanic | +5 | 73.2 m | 1 · National |
| kvkKorean Sign Language한국 수화 언어 | kvk | — | | 180,000 | 4 · Educational |
| coeKoreguaje | coe | Tucanoan | | 2,100 | 6a · Vigorous |
| okhKoresh-e Rostam | okh | Indo-European | | | 7 · Shifting |
| kfqKorku | kfq | Austroasiatic | | 478,000 | 5 · Developing |
| vkpKorlai Portuguese Creole | vkp | — | | 800 | 6a · Vigorous |
| kfoKoro | kfo | Niger–Congo | | | 6a · Vigorous |
| kxrKoro | kxr | Austronesian | | | 6a · Vigorous |
| krfKoro | krf | Austronesian | | | 6a · Vigorous |
| jkrKoro | jkr | Sino-Tibetan | | 1,500 | 6b · Threatened |
| vknKoro Nulu | vkn | Niger–Congo | | | |
| ahsKoro Wachi | ahs | — | | | 6a · Vigorous |
| vkzKoro Zuba | vkz | Niger–Congo | | | |
| kfzKoromfe | kfz | Niger–Congo | | | 5 · Developing |
| kqjKoromira | kqj | South Bougainville | | | 6a · Vigorous |
| bprKoronadal Blaan | bpr | Austronesian | | | 5 · Developing |
| xkqKoronibahasa Koroni | xkq | Austronesian | | | 7 · Shifting |
| krpKorop | krp | Niger–Congo | | | 6a · Vigorous |
| xxrKoropó | xxr | — | | | 10 · Extinct |
| ktlKoroshi | ktl | — | | 1,000 | 8b · Nearly Extinct |
| kheKorowai | khe | Trans–New Guinea | | | 6a · Vigorous |
| kfdKorra Koraga | kfd | Dravidian | | | 6b · Threatened |
| xorKorubo | xor | Pano-Tacanan | | 27 | 8b · Nearly Extinct |
| kpqKorupunbahasa Korapun | kpq | Trans–New Guinea | | | 5 · Developing |
| kfpKorwa | kfp | Austroasiatic | | 570,000 | 6a · Vigorous |
| kpyKoryak | kpy | — | | 3,500 | 6b · Threatened |
| kiqKosarebahasa Kosare | kiq | — | | | 6a · Vigorous |
| kklKosarekbahasa Kosarek | kkl | Trans–New Guinea | | | 5 · Developing |
| bssKose | bss | Niger–Congo | | | 5 · Developing |
| kidKoshin | kid | Niger–Congo | | | 6b · Threatened |
| kosKosraeankahs Kosrae | kos | Austronesian | | 8,000 | 2 · Provincial |
| kfeKota | kfe | — | | | 6a · Vigorous |
| koqKota | koq | Niger–Congo | | | 6a · Vigorous |
| mqgKota Bangun Kutai Malaybahasa Melayu Kota Bangun Kutai | mqg | Austronesian | | | 6a · Vigorous |
| kqkKotafon | kqk | Niger–Congo | | | 6a · Vigorous |
| zkoKott | zko | Yeniseian | | | |
| kvcKove | kvc | Austronesian | | | 6b · Threatened |
| xowKowaki | xow | Trans–New Guinea | | | 8b · Nearly Extinct |
| kwhKowiaibahasa Adi | kwh | Austronesian | | | 6b · Threatened |
| kqdKoy Sanjaq Syriac | kqd | Afroasiatic | | | 6b · Threatened |
| kffKoya | kff | — | | | 5 · Developing |
| khqKoyra Chiini | khq | Nilo-Saharan | | | 4 · Educational |
| sesKoyraboro Senni | ses | Nilo-Saharan | | | 5 · Developing |
| koyKoyukonDenaakk’e | koy | Na-Dene | | 300 | 8a · Moribund |
| kpkKpan | kpk | Niger–Congo | | | 6a · Vigorous |
| cpoKpee | cpo | Niger–Congo | | | 6b · Threatened |
| kpeKpelle | kpe | Niger–Congo | | | |
| kphKplang | kph | Niger–Congo | | | 6a · Vigorous |
| kpoKposo | kpo | Niger–Congo | | | 5 · Developing |
| briKpwe | bri | Niger–Congo | | 32,000 | 6b · Threatened |
| kyeKrache | kye | Niger–Congo | | | 5 · Developing |
| xraKrahô | xra | — | | | 6a · Vigorous |
| rkaKraol | rka | Austroasiatic | | | 6a · Vigorous |
| kqqKrenak | kqq | — | | | 8a · Moribund |
| krsKresh | krs | Nilo-Saharan | | | 5 · Developing |
| zkvKrevinian | zkv | Uralic | | | |
| xreKreye | xre | — | | | 9 · Dormant |
| xriKrikati-Timbira | xri | — | | | 6a · Vigorous |
| krmKrim | krm | Niger–Congo | | | Critically endangered |
| kriKrio | kri | — | | 692,000 | 3 · Wider Communication |
| xkeKrio Dayak | xke | — | | | 6b · Threatened |
| ropKriol | rop | — | | | 3 · Wider Communication |
| mcmKristang | mcm | — | | 800 | 6b · Threatened |
| kxbKrobu | kxb | Niger–Congo | | 9,920 | 6a · Vigorous |
| kgoKrongo | kgo | Niger–Congo | | | 5 · Developing |
| jctKrymchak | jct | Turkic | | 785 | 8b · Nearly Extinct |
| kryKryts | kry | Northeast Caucasian | | 10,000 | 6b · Threatened |
| tyuKua | tyu | Khoisan | | | 6b · Threatened |
| xnhKuan | xnh | Austroasiatic | | | 6b · Threatened |
| uanKuan | uan | — | | | 6b · Threatened |
| ughKubachi | ugh | Northeast Caucasian | | | |
| kgfKube | kgf | Trans–New Guinea | | | 5 · Developing |
| kofKubi | kof | Afroasiatic | | | 9 · Dormant |
| kvbKububahasa Kubu | kvb | — | | 10,000 | 6b · Threatened |
| lkcKucong | lkc | Sino-Tibetan | | | 7 · Shifting |
| kywKudmali | kyw | Indo-European | | | 6a · Vigorous |
| kovKudu-Camo | kov | Niger–Congo | | | 8b · Nearly Extinct |
| kowKugama | kow | Niger–Congo | | | 6a · Vigorous |
| kesKugbo | kes | Niger–Congo | | | 6b · Threatened |
| sbsKuhane | sbs | Niger–Congo | | | 6a · Vigorous |
| fayKuhmareyi | fay | — | | 100,000 | 7 · Shifting |
| ukiKui | uki | — | | 645,000 | 6b · Threatened |
| kvdKuibahasa Kui | kvd | Trans–New Guinea | | | 6b · Threatened |
| vkjKujargé | vkj | — | | | 7 · Shifting |
| kfnKuk | kfn | Niger–Congo | | | 6b · Threatened |
| kuxKukatja | kux | Australian Aboriginal languages | | | 6b · Threatened |
| ukvKuku | ukv | Nilo-Saharan | | | |
| xmhKuku-Muminh | xmh | Australian Aboriginal languages | | | 9 · Dormant |
| uwaKuku-Uwanh | uwa | Australian Aboriginal languages | | | 10 · Extinct |
| kkwKukuya | kkw | — | | 38,800 | 6a · Vigorous |
| tpgKulabahasa Kula | tpg | Trans–New Guinea | | | 6a · Vigorous |
| kulKulere | kul | Afroasiatic | | | 6a · Vigorous |
| xpkKulino | xpk | Pano-Tacanan | | 32 | 8a · Moribund |
| vklKulisusu | vkl | Austronesian | | | 6a · Vigorous |
| kfxKullui | kfx | — | | | 6a · Vigorous |
| bbuKulung | bbu | Niger–Congo | | | 6a · Vigorous |
| kleKulung | kle | Sino-Tibetan | | | 6b · Threatened |
| neeKumak | nee | Austronesian | | | 6b · Threatened |
| kslKumalu | ksl | Austronesian | | | 6a · Vigorous |
| kdiKumam | kdi | — | | | 6a · Vigorous |
| kueKuman | kue | Trans–New Guinea | | | 3 · Wider Communication |
| kfyKumaoniकुमाऊँनी | kfy | Indo-European | | 2.3 m | 5 · Developing |
| kmjKumarbhag Paharia | kmj | Dravidian | | | 6a · Vigorous |
| kgsKumbainggar | kgs | Australian Aboriginal languages | | 90 | 6b · Threatened |
| wkbKumbaran | wkb | Dravidian | | | 6b · Threatened |
| xksKumbewahabahasa Kumbewaha | xks | Austronesian | | | 6a · Vigorous |
| kraKumhali | kra | Indo-European | | | 6b · Threatened |
| kumKumykкъумукъ тил | kum | Turkic | | 426,212 | 5 · Developing |
| zumKumzari | zum | Indo-European | | | 8a · Moribund |
| kunKunama | kun | — | | | 4 · Educational |
| kdnKunda | kdn | Niger–Congo | | 157,000 | 6b · Threatened |
| shdKundal Shahi | shd | — | | 3,371 | 8a · Moribund |
| wkuKunduvadi | wku | Dravidian | | | 6b · Threatened |
| kflKung | kfl | Niger–Congo | | | 8a · Moribund |
| ggkKungarakany | ggk | Australian Aboriginal languages | | | |
| kglKunggari | kgl | Australian Aboriginal languages | | | 9 · Dormant |
| lkuKungkari | lku | Australian Aboriginal languages | | | 10 · Extinct |
| kseKuni | kse | — | | | 5 · Developing |
| xugKunigami山原言葉 | xug | Japonic | | 5,000 | 7 · Shifting |
| kupKunimaipa | kup | Binanderean–Goilalan | | | 5 · Developing |
| kjnKunjen | kjn | Australian Aboriginal languages | | | 8b · Nearly Extinct |
| ktoKuot | kto | — | | | 4 · Educational |
| mknKupang Malay | mkn | Austronesian | | | 3 · Wider Communication |
| keyKupia | key | Indo-European | | | 6b · Threatened |
| kuvKur | kuv | Austronesian | | | 6b · Threatened |
| nqkKura Nago | nqk | Niger–Congo | | | 6a · Vigorous |
| krhKurama | krh | Niger–Congo | | | 6a · Vigorous |
| knkKuranko | knk | Niger–Congo | | | 5 · Developing |
| kurKurdishZimanê Kurdî | kur | Indo-European | +5 | 21 m | Safe |
| nbnKuribahasa Modan | nbn | Austronesian | | | 7 · Shifting |
| kujKuria | kuj | Niger–Congo | | | 5 · Developing |
| kfhKurichiya | kfh | Dravidian | | | 6b · Threatened |
| kmrKurmanjiZimanê Kurdî | kmr | Indo-European | +3 | 14.6 m | 3 · Wider Communication |
| unnKurnai | unn | Australian Aboriginal languages | | | 8b · Nearly Extinct |
| vkuKurrama | vku | Australian Aboriginal languages | | | 8b · Nearly Extinct |
| ktmKurti | ktm | Austronesian | | | 4 · Educational |
| xkzKurtöp | xkz | Bodish | | 15,000 | 6b · Threatened |
| kyrKuruáya | kyr | Tupian | | | 9 · Dormant |
| kjrKurudubahasa Kurudu | kjr | — | | | 6b · Threatened |
| kruKurukh | kru | Dravidian | | 2 m | 5 · Developing |
| kusKusaal | kus | Niger–Congo | +1 | 121,000 | 5 · Developing |
| ksgKusaghe | ksg | Austronesian | | | 6a · Vigorous |
| kuhKushi | kuh | Afroasiatic | | 11,000 | 6a · Vigorous |
| ksvKusu | ksv | Niger–Congo | | | 6a · Vigorous |
| kggKusundaMihaq | kgg | — | | 7 | 8b · Nearly Extinct |
| ghtKutang | ght | Bodish | | | 6a · Vigorous |
| kfrKutchi language | kfr | Sindhi languages | | 866,000 | 6a · Vigorous |
| kubKuteb | kub | Niger–Congo | | | 5 · Developing |
| kutKutenai | kut | — | | 100 | 8a · Moribund |
| xutKuthant | xut | Australian Aboriginal languages | | | 10 · Extinct |
| kpaKutto | kpa | Afroasiatic | | | 6b · Threatened |
| kdcKutu | kdc | Niger–Congo | | 45,000 | 6b · Threatened |
| khjKuturmi | khj | Niger–Congo | | | 6a · Vigorous |
| thdKuuk Thaayorre | thd | Australian Aboriginal languages | | | 6b · Threatened |
| ukyKuuk Yak | uky | Australian Aboriginal languages | | | 10 · Extinct |
| kuyKuuku Ya'u | kuy | Australian Aboriginal languages | | | 8b · Nearly Extinct |
| oluKuvale | olu | Niger–Congo | | | 6a · Vigorous |
| kxvKuvi | kxv | — | | 350,000 | 5 · Developing |
| kdtKuy | kdt | Austroasiatic | | 488,900 | 6b · Threatened |
| fkvKvenkvääni | fkv | Uralic | | 2,000 | 8a · Moribund |
| wkaKw'adza | wka | Afroasiatic | | | 10 · Extinct |
| bkoKwa’ | bko | Niger–Congo | | | 7 · Shifting |
| ksqKwaami | ksq | Afroasiatic | | | 6a · Vigorous |
| kwzKwadi | kwz | Khoisan | | | 10 · Extinct |
| kwpKwadia | kwp | Niger–Congo | | | 6b · Threatened |
| kwdKwaio | kwd | Austronesian | | | 5 · Developing |
| kwuKwakum | kwu | Niger–Congo | | | 6a · Vigorous |
| kwkKwakʼwala | kwk | Wakashan | | 500 | 8a · Moribund |
| qwtKwalhioqua-Clatskanie | qwt | Na-Dene | | | |
| kmqKwama | kmq | Nilo-Saharan | | 319 | 5 · Developing |
| kwmKwambi | kwm | Niger–Congo | | | 5 · Developing |
| tnkKwamera | tnk | Austronesian | | | 5 · Developing |
| okkKwamtim One | okk | Torricelli | | | 6b · Threatened |
| kviKwang | kvi | Afroasiatic | | | 6a · Vigorous |
| kwjKwanga | kwj | Sepik | | | 5 · Developing |
| kwnKwangali | kwn | Niger–Congo | | | 4 · Educational |
| knpKwanja | knp | Niger–Congo | | | 5 · Developing |
| kuaKwanyama | kua | Niger–Congo | | 247,000 | 3 · Wider Communication |
| kwfKwara'ae | kwf | Austronesian | | | 5 · Developing |
| wosKwasengen | wos | Sepik | | | 5 · Developing |
| nmgKwasio | nmg | Niger–Congo | | | 5 · Developing |
| cwtKwatay | cwt | Niger–Congo | | | 5 · Developing |
| xwaKwaza | xwa | — | | 54 | 8b · Nearly Extinct |
| xwgKwegu | xwg | Nilo-Saharan | | | 8a · Moribund |
| kwrKwerbahasa Kwer | kwr | Trans–New Guinea | | | 6b · Threatened |
| kweKwerbabahasa Airmati | kwe | Tor-Kwerba | | | 6b · Threatened |
| xwrKwerba Mamberamobahasa Kwerba Mamberamo | xwr | Tor-Kwerba | | | 6a · Vigorous |
| cweKwere | cwe | Niger–Congo | | 98,000 | 6b · Threatened |
| kkbKwerisabahasa Kwerisa | kkb | Lakes Plain | | | 8b · Nearly Extinct |
| kwsKwese | kws | Niger–Congo | | | 6a · Vigorous |
| kwtKwestenbahasa Kwesten | kwt | Orya–Tor | | | 7 · Shifting |
| kucKwinsubahasa Ansudu | kuc | Orya–Tor | | | 6b · Threatened |
| kwwKwinti | kww | — | | 130 | 6b · Threatened |
| kmoKwoma | kmo | Sepik | | | 5 · Developing |
| kwoKwomtari | kwo | — | | | 5 · Developing |
| aueǂKxʼauǁʼein | aue | Khoisan | | 7,000 | |
| kqlKyenele | kql | Yuat | | | 6a · Vigorous |
| kgyKyerung | kgy | — | | | 6b · Threatened |
| acdKyode | acd | Niger–Congo | | | 5 · Developing |
| cryKyoli | cry | Niger–Congo | | | 6b · Threatened |
| kirKyrgyzКыргыз тили | kir | Turkic | | 4.6 m | 1 · National |