Emperor Duānzōng (端宗, 1268-May 8, 1278) was the penultimate emperor of Southern Song Dynasty of China who died a boy. He was also known as Lord Establishing-Nation (建國公).

Born Zhào Shì (趙是), he was the child of Emperor Gong. He became Prince Ji (吉王) in 1274 and Prince Yi (益王) in 1276. Enthroned at Fuzhou on June 14, 1276, his reign had the era name of Jǐngyán (景炎). He died at Gangzhou.

He was succeeded by his younger brother, Emperor Bing.