Vatican Observatory, Astronomical observatory in Castel Gandolfo, Vatican State.

The Vatican Observatory is an astronomical research facility in Castel Gandolfo, Vatican State. The complex sits on a hilltop and includes a dome containing a refractor telescope.

The Gregorian Tower, built 1578–1580 for the calendar reform promulgated in 1582, is the observatory's origin. Pope Leo XIII formally re-founded the Specola Vaticana with the motu proprio Ut mysticam on 14 March 1891, naming Father Francesco Denza first director. In 1935 Pope Pius XI moved it to the Papal Palace at Castel Gandolfo because Rome's sky-glow hindered observations.

The observatory is run by the Society of Jesus, and its staff include Jesuit priests and brothers. Its meteorite collection, built up over decades, supports spectroscopic laboratory work at Castel Gandolfo. The name Specola Vaticana comes from the Italian word for observatory, and the institution's instruments have been donated or acquired through benefactors since 1891.

The observatory's headquarters occupy a former convent about a mile from the papal palace in Castel Gandolfo, where four domes stand: two wooden ones on the palace roof and two connected domes in the palace gardens. The Carte du Ciel telescope, installed in 1891 on the Tower of St. John and moved here in 1942, sits in the garden domes. The instruments only partly meet modern requirements, and the working site is reached through organised visits rather than open access.

The institution operates a second research site in Arizona since the early 1990s, equipped with an advanced telescope for deeper sky observations. This transatlantic collaboration allows research under better atmospheric conditions.