Penteli Observatory, Astronomical observatory in Penteli, Greece.

Penteli Observatory is an astronomical facility on Mount Penteli equipped with telescopes and measurement instruments for observing the sky. The station conducts research and supports scientific studies of celestial objects and cosmic phenomena.

The Penteli Astronomical Station was established in 1937. In 1955 the National Observatory of Athens accepted the Thomas Cooke refractor, built in 1869 for Newall, from Cambridge University; it was dismantled and shipped to Piraeus in 1957 and installed in 1958 in a building made entirely of Pentelic marble. The observatory itself was founded in 1958 as part of the National Observatory of Athens.

The National Observatory of Athens maintains this facility as a center for astronomy education, offering programs that connect the public with space sciences.

The site sits on Koufos hill on Mount Penteli at 500 m, near Nea Penteli, and can be reached only by car. The visitor centre of the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing has operated here since 1995, running seminars, lectures and night observations with the Newall telescope.

The 63 cm Thomas Cooke refractor was built in 1869 for Newall and donated to Cambridge in 1890. Cambridge passed it on, and the National Observatory of Athens accepted it in 1955; it was dismantled and shipped to Piraeus in 1957. It is no longer used for scientific research.