| KNUE Astronomical Observatory | Corea del Sur | Sejong | — |
| Kochi observatory | Japón | Kōchi | — |
 Kodaikanal Solar Observatory | India | Kodaikanal | — |
| Koeditz observatory | Alemania | Köditz | — |
| Kogota observatory | Japón | Kogota | — |
| Koksijde observatory | Bélgica | Koksijde | — |
| Komakallio observatory | Finlandia | Kirkkonummi | — |
| Konan observatory | Japón | Konan | — |
| Konigsleiten observatory | Austria | Wald im Pinzgau | — |
 Kopernik Space Center | Estados Unidos | Vestal | 530 m |
 Korea Advanced Institute of Science and Technology Satellite 4 | Corea del Sur | — | — |
| Korea Microlensing Telescope Network-CTIO | Chile | Piedras Blancas | — |
| Korea Microlensing Telescope Network-SAAO | Sudáfrica | Karoo Hoogland | — |
| Korea Microlensing Telescope Network-SSO | Australia | Coonabarabran | — |
 Koronas-Foton | — | — | — |
| Koschny Observatory | Países Bajos | Noordwijkerhout | — |
| Kosi Bird Observatory | Nepal | — | — |
| Kottamia Astronomical Observatory | Egipto | El Cairo | 482 m |
| Kouba Observatory | Argelia | Argel | — |
| Kourou Magnetic Observatory | Francia | — | — |
 Kourovskaya observatory | Rusia | Sverdlovsk | 280 m |
 Koyama Astronomical Observatory, Kyoto Sangyo University | Japón | Kita-ku | — |
| Kramatorsk Observatory | Ucrania | Óblast de Donetsk | 76 m |
| Krasnodar observatory | Rusia | — | — |
 Kremsmünster Observatory | Austria | Kremsmünster | 382 m |
 Kryoneri Observatory | Grecia | Sikyona | — |
 Kryzhanivka Observatory | Ucrania | Fontanka rural hromada | 40 m |
| KSA SEM observatory | Corea del Sur | Busan | — |
| KU Observatory | Pakistán | Karachi | 5.000 m |
| Kuban State University Astrophysical Observatory | Rusia | Krai de Krasnodar | 71 m |
 Kuiper Airborne Observatory | Estados Unidos | — | — |
| Kuiper Telescope | Estados Unidos | Pima County | 2.510 m |
 Kulin Observatory | Hungría | Újpest | — |
| Kuma Kogen Astronomical Observatory | Japón | Kumakōgen | 609 m |
| Kumagaya City Cultural Center Planetarium Hall | Japón | Kumagaya | — |
| Kumamoto | Japón | prefectura de Kumamoto | — |
 Kumamoto Civil Astronomical Observatory | Japón | Minami-ku | — |
 Kurashiki Observatory | Japón | Kurashiki | — |
| Kure City Kamagari Astronomical Observatory | Japón | Kure | — |
| Kurihara observatory | Japón | Kurihara | — |
| Kuriwa observatory | Australia | Hawkesbury Heights | — |
| Kurohone observatory | Japón | Kurohone | — |
| Kurume City Observatory | Japón | prefectura de Fukuoka | — |
| Kushiro observatory | Japón | Kushiro | — |
| KUSZA Observatory | Malasia | Terengganu | — |
 Kvant-1 | — | — | — |
 Kwasan | Japón | Yamashina-ku | — |
| KYSUCE observatory | Eslovaquia | Kysucké Nové Mesto | — |