Emperor Xiaozong of Song (27 November 1127 – 28 June 1194), personal name Zhao Shen, courtesy name Yuanyong, was the 11th emperor of the Song dynasty of China and the second emperor of the Southern Song dynasty. He started his reign in 1162 when his adoptive father and predecessor, Emperor Gaozong, abdicated and passed the throne to him. Even though Emperor Gaozong became a Taishang Huang ("Retired Emperor") after his abdication, he remained the de facto ruler, so Emperor Xiaozong only took full power in 1187 after Emperor Gaozong's death. After ruling for about a year, Emperor Xiaozong followed in his predecessor's footsteps and abdicated in favour of his third son Zhao Dun (Emperor Guangzong), while he became Taishang Huang and still remained in power until his death in 1194.

He was the first descendant of Emperor Taizu to become emperor and remembered as an effective ruler as the Song enjoyed prosperity during his reign.

Zhao Shen's birth name was Zhao Bocong (趙伯琮). In March 1133, after Zhao Bocong entered the imperial palace, his name was changed to Zhao Yuan (趙瑗). In April 1160, after Zhao Yuan was adopted by Emperor Gaozong, his name was changed to Zhao Wei (趙瑋). In July 1162, when Zhao Wei became crown prince, his name was changed again to Zhao Shen (趙眘).

Zhao Shen was given the courtesy name Yuangui (元瑰) in May 1160. In July 1162, when he became crown prince, his courtesy name was changed to Yuanyong (元永).

Zhao Shen was a seventh-generation descendant of Emperor Taizu, the founder and first emperor of the Song dynasty. He was the second son of Zhao Zicheng (趙子偁; died 1143), a sixth cousin of Emperor Gaozong, the 10th Song emperor. After the Jingkang Incident in 1127, Emperor Gaozong's father, eldest brother and most of his close relatives were taken prisoner by the Jurchen-led Jin Empire. As Emperor Gaozong's only son, Zhao Fu (趙旉), died prematurely around the age of two, the emperor ordered his officials to start searching for other living descendants of the imperial family. Zhao Shen was discovered and adopted by Emperor Gaozong in April 1160 as a son. Another relative, Zhao Qu was also adopted. In July 1162, Emperor Gaozong officially designated Zhao Shen as his crown prince and heir apparent. One of the main reasons Gaozong chose Shen over Qu was of Shen's virtue. It is said that Gaozong gave ten maids to Shen and Qu. In the end, Qu had touched every maid but Shen had not even touched one winning Gaozong's favor over Qu.

In 24 July 1162, Emperor Gaozong abdicated in favor of Emperor Xiaozong who became emperor although Emperor Gaozong retained power as Taishang Huang.

During the reign of Emperor Xiaozong, the Chinese increased the number of trade missions that would dock at ports throughout the Indian Ocean, where Arab and Hindu influence was once predominant. Xiaozong also was responsible for Yue Fei's posthumous rehabilitation, clearing out the remnants of Qin Hui's faction in court, and stabilizing the economy making his reign the most powerful era of the Southern Song Dynasty and it's said he was the best ruler of the Southern Song dynasty.

Xiaozong's reign was one of the few times in Southern Song that was not dominated by powerful officials, as he held power supreme and unchallenged. He was also a demanding emperor who frequently dismissed ministers without hesitation if they failed to meet his expectations. This led to many criticisms of the emperors personnel policy. In 1166, the lesser lord of agricultural supervision, Mo Chi remonstrated to the emperor, criticizing him for dismissing councilors and other officials only having served for a few months. The emperor commended Mo Chi for his criticism, but ignored it. One of the reasons behind Xiaozongs policy could have been to avoid the amassing of great power in the person of individual officials, such as the great power wielded by Qin Gui in Gaozong's era, with a convenient way in achieving this to limit ministerial tenure of office so they could not build a base in court.