Helena Palaiologina (; 23 April 1442 – 1469) was the daughter and only child of Demetrios Palaiologos, Despot of Morea, a brother of the final Byzantine emperor Constantine XI Palaiologos. Her mother was Theodora Asanina of the Asen family, a family which had once ruled Bulgaria. Famous for her beauty, Sultan Mehmed II, who had conquered Constantinople in 1453, planned to take her into his harem after his conquest of the Morea in 1460, but soon decided against it, despite securing Helena and her family, possibly due to fear of being poisoned by her.