Emperor Duanzong of Song (10 July 1269 – 8 May 1278), personal name Zhao Shi, was the 17th emperor of the Song dynasty in China and the eighth emperor of the Southern Song dynasty. He was the fifth son of Emperor Duzong and an elder brother of his predecessor, Emperor Gong and successor Zhao Bing.
Emperor Gong along with Grand Dowager Xie surrendered to the Mongol Empire in 1276 after the fall of the Song capital, Lin'an (present-day Hangzhou). Zhao Shi and his seventh brother, Zhao Bing, managed to escape southward to Fujian Province, where the new Song capital was established. On June 14, 1276, Zhao Shi was enthroned as the new Emperor Duanzong who ruled under the era name "Jingyan" (景炎; literally: "bright flame"). However, in 1278, the Mongols broke through the Song dynasty's last lines of defence, forcing Zhao Shi to flee again. Accompanied by loyal ministers such as Lu Xiufu and Zhang Shijie, Zhao Shi boarded a ship and fled further south to Guangdong Province. Thereafter, he stayed temporarily in Hong Kong which at that time was a small fishing village. The historical relic Sung Wong Toi in present-day Hong Kong's Kowloon City commemorates Zhao Shi's escape to Hong Kong.
In March 1278, while fleeing from the Mongols led by Liu Shen, in a hurricane, Zhao Shi fell from a boat and almost drowned. After his rescue, he became ill and died a few months later in Gangzhou (碙州; present-day Lantau Island, Hong Kong). He was succeeded by his seventh brother, Zhao Bing.