Konkoly Observatory (Hungarian: HUN-REN Csillagászati és Földtudományi Kutatóközpont Konkoly Thege Miklós Csillagászati Intézet; obs. code: 053) is an astronomical observatory located in Budapest, Hungary is part of the Research Centre for Astronomy and Earth Sciences (Hungarian: Csillagászati és Földtudományi Kutatóközpont) and belongs to the HUN-REN Magyar Kutatási Hálózat. Konkoly Observatory was founded in 1871 by Hungarian astronomer Miklós Konkoly-Thege (1842–1916) as a private observatory, and was donated to the state in 1899. Konkoly Observatory, officially known as HUN-REN CSFK Konkoly Thege Miklós Csillagászati Intézet in Hungarian, is the largest astronomical research institute in Hungary, and hosts the largest telescopes in the country. The Observatory has more than 60 researchers, a quarter of them are non-Hungarian.

The main research areas include stellar structure and evolution, stellar and solar activity, variable stars, star and planetary formation, interstellar material, exoplanets, cosmology, large sky survey, Solar System studies, nuclear and extragalactic astrophysics, high energy astrophysics including supernovae, gamma-ray bursts and other transient events, radio astronomy, galactic archeology, designing and manufacturing astronomical instrumentation and cubesats, as well as history of astronomy. The institute has a close collaboration with Hungarian universities, the researches teach and supervise students at ELTE and Szeged Universities. Konkoly Observatory runs the assistant researcher (Hungarian: demonstrátor program introducing undergraduate students to scientific research and using astronomical telescopes and instruments. The Observatory hosted 7 Lendület-grants, 2 ERC-projects and several national large infrastructure projects (GINOP).

As well as performing astronomical research, the observatory published the Information Bulletin on Variable Stars on behalf of the International Astronomical Union.

Hungarian nobleman Miklós Konkoly-Thege founded his private observatory in 1871 at Hurbanovo, in Northern Hungary, known as Ógyalla in Hungarian at the time. The instrumentation included a 6" refractor, a 10.5" Browning reflector (later replaced with a 10" Merz refractor), a meridian circle, a spectrograph, as well as various meteorological and geomagnetic instruments. Konkoly-Thege, who had no offspring, became increasingly afraid over time that his legacy will perish with his death. As a member of the Hungarian Parliament, he was able to convince the government to take the observatory into state property. In 1899, the Hurbanovo site was renamed to Royal Konkoly-founded Astrophysical Observatory, and operated under the direction of Konkoly-Thege and Radó Kövesligethy, a renowned geophysicist of the time. The main scientific profile of the institute was the photometry of stars, the observation of the Sun, meteor counting, and providing time service for the government. In 1913, an order for a 60 cm (24") telescope was finalized with the German Heyde company, but with the start of World War I, the telescope was never built.

After the end of World War I, Ógyalla became part of the newly formed Czechoslovak Republic. The government transferred the scientific equipment to Budapest before the newly formed border was shut down, and in 1921 allocated a new property in the Buda Hills just west to Budapest to build a new astronomical observatory. The new building, known as the Svábhegy observatory after a nearby hill, was finished by 1924, and the 6" refractor and the re-ordered 60 cm Heyde telescope were set up in new domes by 1928. Scientific work in the observatory focussed on the light variations of pulsating stars, the orbits of binary stars, and searching for asteroids. Measurements were made with photographic plates and wedge photometers.

The observatory survived World War II with minor damages. In late 1944, observations were put on hold, and the optical elements of the telescopes were removed to protect them from aerial bombings. Soviet troops occupied the buildings from December 1944 until February 1945, but the library and the photographic laboratories were spared. Observations were resumed by July 1945.

After the communist takeover of Hungary in 1948, a new network of research institutes, independent from universities, was set up under the Hungarian Academy of Sciences (HAS). The observatory was renamed to the Astronomical Institute of the HAS, but retained the traditional name, Konkoly Observatory, in English correspondences. With the communist isolation of the country, international relations shifted from predominantly German and American to Soviet and Eastern-bloc partnerships. However, the international recognition of then director László Detre kept some connections to the West alive. During one of his visits to the Western bloc, Detre received an RCA 1P21 photomultiplier tube from American astronomer Harlow Shapley to start photometric measurements at the observatory in 1948. He subsequently smuggled in to the country despite the strict trade restrictions at the time. In 1957, after the launch of Sputnik, multiple independent satellite observing and tracking stations were set up in the country at the suggestion of the Soviet Union. The institute provided coordination for these stations, and in 1966, the Baja station merged into the institute.

Relations with the West soon eased and at the 1961 General Assembly of the International Astronomical Union at Berkeley, the institute was tasked with setting up and circulating the Information Bulletin on Variable Stars. The Bulletin was envisaged to be a rapid communications platform between variable star observers, but it later expanded into a peer-reviewed journal for short papers and notes about variable stars.