Prince Tsunesada

Prince Tsunesada 恒貞親王
Crown Prince of Japan
Illustration by Kikuchi Yōsai, from Zenken Kojitsu
Crown Prince (皇太子, Kōtaishi?)
Reign	833–842
Coronation	833
Born	825
Died	October 12, 884
Father	Emperor Junna
Mother	Princess Seishi

Prince Tsunesada (恒貞親王, Tsunesada-shinnō^?, 825 – October 12, 884) was a Japanese prince of the early Heian period. He was the second son of Emperor Junna. He was also known as Prince Teishi (亭子親王^?), and by his Buddhist name of Gōjyaku (恒寂^?).

After the death of his older half-brother Prince Tsuneyo (恒世親王^?), Tsunesada became Emperor Junna's successor. In 833, his cousin Emperor Ninmyō took the throne, and by the wishes of the retired emperor Saga, Tsunesada became Crown Prince. In 838, Tsunesada underwent the genbuku rite of passage in the shishin-den (紫宸殿^?) palace, at which he is said to have shown good manners, and cut a graceful figure as he expressed his gratitude to the Emperor. After this, Tsunesada and the retired Emperor Junna became anxious about being embroiled in a power struggle and repeatedly petitioned to resign, but Saga and Ninmyō dissuaded them each time. However, after the Jōwa Incident immediately following Saga's death in 842, Tsunesada was disinherited as crown prince.