Xiao Song (Chinese: 蕭嵩; pinyin: Xiāo Sōng; died 749), formally the Duke of Xu (徐公), was an official and general of the Chinese Tang dynasty, serving as a chancellor during the reign of Emperor Xuanzong.
It is not known when Xiao Song was born. His family was descended from the imperial family of Liang Dynasty. Hiis great-great-grandfather was Emperor Ming of Western Liang, and his great-granduncle Xiao Yu was a famed chancellor during the reigns of Tang Dynasty's first two emperors, Emperor Gaozu and Emperor Taizong. Xiao Song's grandfather Xiao Jun (蕭鈞) was well known as a deputy head of the legislative bureau of government (中書省, Zhongshu Sheng) and Xiao Song's father Xiao Guan (蕭灌) served as a prefectural secretary general.
Xiao Song himself was described as handsome and tall, with a lengthy and beautiful beard. His wife was a daughter of one He Hui (賀晦), another daughter of whom married Lu Xiangxian. At that time, Lu, who was the son of the chancellor Lu Yuanfang, was already well known for his abilities while serving as the sheriff of Luoyang County—one of the two counties making up the then-capital Luoyang, while Xiao was not yet serving as an official. The guests were all rushing to greet Lu, while not paying much attention to Xiao. However, a fortuneteller, Xia Rong (夏榮), stated to Lu, "You, Master Lu, will reach the apex of officialdom in 10 years. However, Master Xiao's household will be thoroughly honored, and he will reach high positions and have a long life."