Theodore Spandounes (Greek: Θεόδωρος Σπανδούνης, Italian: Teodoro Spandugino) was an early 16th-century Greek historian of noble Byzantine extraction, the son of exiles fleeing the Ottoman conquest of Byzantium who had settled in Venice in Italy. As a youth he stayed with relatives in Ottoman-ruled Macedonia and visited the Ottoman capital at Constantinople, acquiring a knowledge of their history and culture. In later life he served successive Popes as a counsellor and repeatedly advocated the dispatch of a new Crusade against the Ottomans. His chief legacy is his Italian-language history on the origins of the Ottoman state and its history up to that time, whose first version was published in 1509 in Italian and was soon translated into French. Spandounes continued working on it, with the final version appearing in 1538. The work is disorganized and contains errors, but is extremely valuable as a historical source for its wealth of information.
Theodore Spandounes was most probably born in Venice, the son of Matthew Spandounes and Eudokia Kantakouzene. His father was a Greek soldier who entered the service of the Venetian Republic as a stradioti mercenary, and for unspecified exploits was raised to the title of Count and Imperial Knight of the Holy Roman Empire by Emperor Frederick III in 1454. He was also given a grant of land around the town of Loidoriki in Greece. This was a nominal grant meant as a gesture of honour, since the territory in question was under Ottoman control, but according to historian Donald Nicol it is possibly indicative of the Matthew's and his family's place of origin. On the other hand, both Spandounes and other members of the family still remaining in the Ottoman-ruled Balkans claimed descent from Constantinople itself, while some had settled in Venice as early as the 1370s. Theodore's mother was a descendant of the Kantakouzenoi, one of the most notable late Byzantine aristocratic lines, which had produced a number of emperors as well as rulers of the Despotate of the Morea in the Peloponnese. Apart from Theodore, the couple had at least two more children: a daughter, who married the Venetian citizen Michael Trevisan, and a son, Alexander, who became a merchant.