Konstantinos Graitzas Palaiologos (Greek: Κωνσταντίνος Γραίτζας Παλαιολόγος) was the commander of the Byzantine garrison at Castle Salmeniko near Patras during the invasion of the Despotate of Morea by the forces of Mehmed II of the Ottoman Empire in 1460–61.
Whereas Thomas fled to Modon, Corfu, and finally to Rome as a refugee, his brother Demetrios surrendered outright to the Sultan.
After Mehmed's departure however, two successive subordinates disregarded the promise, arresting the first soldiers to leave the citadel and then renewing the siege.
By mid July 1461, the Salmeniko citadel was isolated and surrounded and, as the last garrison of the Roman Empire, without hope of relief.
With the Roman Empire he served having ceased to exist, Graitzas accepted a commission as a general in the armed forces of the Republic of Venice.