Thomas Kantakouzenos (Greek: Θωμάς Καντακουζηνός, Thomás Kantakouzenós, modern pronunciation Thomás Kantakouzinós, Serbian: Тома Кантакузин/Toma Kantakuzin; died 25 July 1463) was a Byzantine aristocrat, a member of the Kantakouzenos family, who became a Serbian magnate and general that served Despot Đurađ Branković.
The Byzantinist Donald Nicol, who researched the family's history, categorically identifies him as the brother of George Palaiologos Kantakouzenos; Giovanni Musachi makes him the brother of Irene Kantakouzene, wife of Serbian Despot Đurađ Branković, but incorrectly states Thomas was the son of the Emperor John VI Kantakouzenos, an error DuCange repeats.
Despite this ceremony, Kantakouzenos carried on the fight on behalf of his brother-in-law, leading the Despot's army to victory over Bosnian king Stephen Thomas on 16 September 1448, which restored Srebrenica and Višegrad to Serbian rule.
[3] Despite his position, following Đurađ Branković's death Thomas was unable to shield his sister Irene from the cruelty of her son Lazar.
On the night of Irene's death, 3 May 1457, he fled from Smederevo to Ottoman-ruled Adrianople with his niece Mara and his blinded nephew Grgur.