Thomais Orsini (born ca. 1330) was the queen consort of the Serbian tsar and ruler of Epirus and Thessaly, Simeon Uroš Palaiologos.
Born Thomais Komnene Angelina in the early 1330s, she lost her father John II Orsini in 1335, when he was poisoned, allegedly by his wife, Anna Palaiologina, a scion of the ruling Palaiologos dynasty of the Byzantine Empire. After John II's death, his wife Anna became regent of the Despotate of Epirus for Thomais' brother, Nikephoros II.
Soon, however, in 1338, the Orsini were evicted from Epirus by the Byzantine emperor Andronikos III Palaiologos, who annexed Epirus to the Byzantine Empire. Nevertheless, during the destructive Byzantine civil war that followed Andronikos III's death in 1341, most of the remaining Byzantine territories, including Epirus and Thessaly, fell to the forces of the Serbian ruler Stephen IV Dušan, who in 1346 founded the Serbian Empire. In 1348, Dušan appointed his younger half-brother, the half-Greek Simeon Uroš Palaiologos, as governor of Acarnania and the southern parts of Epirus.
Orsini is a surname of Italian origin, ultimately derived from Latin ursinus ("bearlike") and originating as an epithet or sobriquet describing the name-bearer's purported strength. Notable people with the surname include:
The Orsini family is an Italian noble family; it was one of the most influential princely families in medieval Italy and renaissance Rome. Members of the Orsini include popes Celestine III (1191–1198), Nicholas III (1277–1280), and Benedict XIII (1724–1730), 34 cardinals and numerous condottieri and other significant political and religious figures.
According to their family legend, the Orsini are descended from the Julio-Claudian family of ancient Rome. This is fanciful, as is the alleged connection to the German families of Anhalt, Baden and Bohemian Rosenberg sporting the same name. The Orsini also carried on a political feud with the Colonna family for centuries in Rome, until it was stopped by Papal Bull in 1511; in 1571 the Chiefs of both families married the nieces of Pope Sixtus V.