Konstantin-Assen, Prince of Vidin, Duke of Saxony
(born 5 December 1967) is the fourth son of Tsar Simeon II of Bulgaria and his wife Doña Margarita Gómez-Acebo y Cejuela.
He is known also as Konstantin-Assen of Bulgaria and Konstantin-Assen of Vidin, the latter being the title of the fourth son of Bulgarian kings.
He was born in Madrid.
Simeon II was exiled as a child when Bulgaria ceased to be a monarchy, so Simeon's wife and children never received any royal titles from Bulgaria.