19th century

Adolphe Quetelet first petitioned the government of the United Kingdom of the Netherlands to establish an astronomical observatory in Brussels in 1823. William I granted his request in 1826 and construction started in 1827 in Saint-Josse-ten-Noode. Meteorological observations started early, but delivery and installation of astronomical equipment proceeded slowly. Quetelet was appointed astronomer in 1828.

During the Belgian Revolution, fighting took place in and around the observatory. Quetelet kept his position under the new government and started scientific observations. By 1834, buildings and instruments were finally completed. Adolpe Quetelet was succeeded by his son Ernest upon his death in 1874.

In 1876, Jean-Charles Houzeau became the new director. He called on François van Rysselberghe to attach him to the weather forecast service the same year. On 26 September 1876, the Observatory published the first Meteorological Bulletin in its history.^[2] Immediately after he became director, Houzeau started planning a move to Uccle. He managed to obtain better funding, enlarged the scientific staff and completely renewed the instruments. The first Belgian astronomical expedition was sent to Santiago and San Antonio to observe the transit of Venus in 1882. He tried to separate the meteorological and astronomical departments, but this was refused by the government. In 1883 construction of a new observatory in Uccle started, but Houzeau's resignation in 1883 delayed the move which was only completed in 1890–1891.

20th century

Georges Lecointe was appointed as director in 1900, succeeding F. Folie and A. Lancaster. Under his leadership, seismological measurements started in 1901 and the first weather balloons were launched in 1906. Belgium participated in the Carte du Ciel and the Astrographic Catalogue; observations lasted until 1964. In 1913 the meteorological department finally became an independent entity, the Royal Meteorological Institute. After World War I the Central Bureau for Astronomical Telegrams was located in Uccle from 1920 to 1922 while it was headed by Lecointe.

Illness forced Lecointe to resign in 1925 and he was succeeded by Paul Stroobant.^[3] Since 1981, the Sunspot Index Data center, the World data center for the Sunspot Index is harbored at the observatory.^[4]

The Planetarium is located on the Heysel Plateau, in the northern region of Brussels.

King Baudouin was an amateur astronomer and took a keen interest in the Royal Observatoy. After his death a statue in honour of the king was raised outside the entrance.