The Kryoneri Observatory (Greek: Αστεροσκοπείο Κρυονερίου), also known as the Kryoneri Astronomical Station (Αστρονομικός Σταθμός Κρυονερίου), is an astronomical obervatory in Greece operated by the IAASARS research institute of the National Observatory of Athens. It is home of one of the largest telescopes in Greece, a 1.23 metres (48 in) Cassegrain reflector, which was used for the NELIOTA project of ESA and NOA. The observatory is also housing smaller instruments that are conducting research for IAASARS and are participating in international programmes.

The Kryoneri Observatory was established in 1972 and in 1975 its first telescope was installed, a 123 centimetres (48 in) Cassegrain reflector manufactured by Grubb Parsons, a British company based in Newcastle. The telescope was financed by the bequest of Marinos Korgialenios, a businessman and national benefactor of Greece who had bequested 200,000 drachmes to the National Observatory of Athens for the purchase of a large equatorial telescope in 1916. At that time the director of the Observatory was Demetrios Eginitis, a personal friend of Korgialenios and on whose request the bequest was given. However, the purchase of the telescope had to be postponed several times due to events like the First World War and the Greco-Turkish War. After the Second World War, Korgialenios' bequest had suffered considerable mutilation and the subsequent distress of the country led Stavros Plakidis, then director of the Οbservatory, to decide that such a purchase could not be made. Finally in 1971, 55 years after Korgialenios bequeathed to the Observatory, Demetrios Kotsakis submitted an application to the Government for 12,000,000 drachmes. So an essential increase of the bequest was effected permitting to start enquires and discussions with a view to buy a telescope of 100 to 120 centimeters, and 4 years later a telescope was installed in the recently established Kryoneri Observatory. This telescope, which still is the main telescope of the observatory, came to be known as the Korgialenio telescope (Greek: Κοργιαλένειο Τηλεσκόπιο) and the observatory is sometimes referred to as the Korgialenios Astronomical Station of Kryoneri (Κοργιαλένειος Αστρονομικός Σταθμός Κρυονερίου).

In 2016, a major upgrade was conducted to the telescope by DFM Engineering, in order for it to be suitable for NELIOTA project. It included its conversion into a prime focus telescope, the replacement of some mechanical parts, the installation of a new control system, an increase of the automation of the dome and the installation of a new instrument.

The Kryoneri Observatory is located in the Corinthia regional unit of the Peloponnese. It was build on Mount Kyllini at an altitude of 930 meters above sea level. The closest settlement is Kryoneri and the observatory is named after it.

The Kryoneri Observatory consists of three buildings:

• The dome building, which hosts the main telescope, the telescope control room and the guest room
• The role-off building, which houses a smaller telescope
• The supporting power generators building

The Korgialenio telescope is one of the largest telescopes in Greece, with only the Aristarchos 2.3m Telescope in the Chelmos Observatory and the 1.3m Telescope in the Skinakas Observatory being larger in size. It is the main telescope of the Kryoneri Observatory and it was manufactured and installed by Grubb Parsons in 1975. It is a Cassegrain reflector with a 123 centimetres (48 in) parabolic primary mirror and a 31 centimetres (12 in) hyperbolic secondary mirror, both of which were created with Zerodur. Its mounting is based on a modified torque-tube equatorial system. The telescope was converted to a prime focus telescope by DFM Engineering in 2016 and its Prime Focus Instrument (PFI) was installed, which is able to provide the large field of view, making it suitable for the NELIOTA project. On the back of the Prime Focus Instrument there are two fast-frame sCMOS Andor Zyla 5.5 cameras offering the ability to record a target simultaneously in two different wavelength bands. The Instrument can also accommodate another option for imaging, hosting a "direct imaging" Apogee Aspen CCD where the light path is directed directly to the prime focus.

The observatory is also housing a smaller telescope of the MAWFC Deep Sky Survey, which is located in a role-off building. Next to this building is one of the stations of the Very Wide Field of View network, which is equipped with a sensor for detecting objects in Low Earth Orbit using Optical Triangulation. It was manufactured by Cilium Engineering and it was installed in November 2021.

A high-power laser transmitter is to be installed in the Kryoneri Observatry as part of NASA's Deep Space Optical Communications system. It will be the only transmitter of the system located in Europe and the goal is to communicate with the Psyche spacecraft in 2026.

The Near-Earth object Lunar Impacts and Optical TrAnsients (NELIOTA) was a research project funded by the European Space Agency from 2017 to 2023 and it aimed to determine the distribution and frequency of small near-earth objects by monitoring lunar impact flashes. For six and a half years the Korgialenio telescope was observing the Moon and detecting flashes on its surface which were caused by near-earth objects colliding with it. Apart from completing its main goal, it also became the largest study on asteroid collisions with the Moon since it was also detecting the size and the mass of the asteroids and the temperature created during the collision.

The National Observatory of Athens has signed a memorandum of understanding with the Polish Space Agency for one of the stations of the Very Wide Field of View (VWFOV) network to be located in the Kryoneri Observatory; and for the IAASARS team to contribute to its operations. The station consists of a sensor developed by Cilium Engineering and it is desined to detect objects in Low Earth Orbit using the Optical Triangulation method. Out of the four such stations, three in Poland and one in Greece, the one at the Kryoneri Observatory was the first to be deployed with its completion occurring on 21 November 2021.

The Manchester-Athens Wide-Field (Narrow-Band) Camera (WAWFC) is a Deep Sky Survey of the extensive line emission regions at high galactic latitudes. It is a joint project of the National Observatory of Athens and the Jodrell Bank Centre for Astrophysics of the Manchester University that aims to conduct a large-area sky survey with the aid of a customized camera and narrow-band filters properly designed for studying extended interstellar medium (ISM) structures in the optical emission lines of Ηα, [O III], and Hβ. The WAWFC building at the Kryoneri Observatory was completed on 1 November 2019.

The National Observatory of Athens had signed a memorandum of understanding with the Europlanet 2024 RI Consortium for the participation of the Kryoneri Observatory in the Europlanet Telescope Network, which was valid until 31 January 2024. As part of the program, the Korgialenio telescope detected lunar impact flashes during the Perseids meteor shower in 2023, using the instruments developed for the NELIOTA project. The results when then combined with the ones from NELIOTA.

The Kryoneri Observatory is one of the observatories chosen by the European Space Operations Center of the European Space Agency for it to observe satellite movements. The goal is to monitor the orbits of satellites for what is known as planetary security, making sure that the chaotic situation occurring around Earth by the thousands of satellites is under control.

A high-power laser transmitter is going to be installed in the Kryoneri Observatory as part of the Deep Space Optical Communications system of NASA. The plan is to fire a high-powered laser to the Psyche spacecraft, which will then send back a response to the Aristarchos Telescope in the nearby Chelmos Observatory. These two observatories in Greece are the only European ones participating in this laser communications demonstration. The experiment is to take place in January 2026.