The Castellania (Maltese: Il-Kastellanija; Italian: La Castellania), also known as the Castellania Palace (Maltese: Il-Palazz Kastellanja; Italian: Palazzo Castellania), is a former courthouse and prison in Valletta, Malta. It was built by the Order of St. John between 1757 and 1760, on the site of an earlier courthouse which had been built in 1572.

The building was built in the Baroque style to design of the architect Francesco Zerafa, and completed by Giuseppe Bonici. It is a prominent building in Merchants Street, having an ornate façade with an elaborate marble centrepiece. Features of the interior include former court halls, a chapel, prison cells, a statue of Lady Justice at the main staircase and an ornate fountain in the courtyard.

From the late 18th to the early 19th century, the building was also known by a number of names, including the Palazzo del Tribunale, the Palais de Justice and the Gran Corte della Valletta. By the mid-19th century the building was deemed too small, and the courts were gradually moved to Auberge d'Auvergne between 1840 and 1853. The Castellania was then abandoned, before being briefly converted into an exhibition centre, a tenant house and a school.

In 1895, the building was converted into the head office of the Public Health Department. The department was eventually succeeded by Malta's health ministry which is still housed in the Castellania. The building's ground floor contains a number of shops, while the belongings of Sir Themistocles Zammit's laboratory are now housed at the second floor and is open to the public by appointment as The Brucellosis Museum.