Konstantinos Graitzas Palaiologos (Greek: Κωνσταντίνος Γραίτζας Παλαιολόγος) was the commander of the Byzantine garrison at Salmeniko Castle near Patras during the invasion of the Despotate of Morea by the forces of Mehmed II of the Ottoman Empire in 1460.
Graitzas descended from an obscure branch of the Palaiologos family, but showed far more valor than his distant relatives, the siblings and co-ruling Despotes Thomas Palaiologos and Demetrios Palaiologos. Whereas the former fled to Modon, Corfu, and finally Rome and the latter surrendered outright to the Sultan, Graitzas maintained his position, holding his redoubt until July 1461, long after the surrender of his lords. Mehmed the Conqueror personally oversaw the attack. The elite Janissaries managed to subdue the town by cutting off its water supply. Its remaining residents (approximately 6000) were sold into slavery, with 900 children chosen for the Devşirme. Graitzas and his garrison continued to hold out in the castle citadel. At this point, Gratizas agreed to surrender the castle to Mehmed in return for safe conduct and immunity for his troops. Following Mehmed's departure however, two successive subordinates disregarded the promise, arresting the first soldiers to leave the citadel and then renewing the siege. In July 1461, with Salmeniko now isolated and surrounded and, as the last garrison of the Roman Empire, no hope of relief, Graitzas, leading a sortie of the remaining garrison, escaped the besiegers and sought refuge in the Venetian fortress of Lepanto (modern Naupactus).