Emperor Gong of Sui (隋恭帝) (605 – 14 September 619), personal name Yang You (楊侑), was an emperor of the Chinese Sui dynasty. He was installed as a puppet emperor by Li Yuan, and after Emperor Yang of Sui died, Li then became the founding emperor of the Tang dynasty and had Yang You executed. Traditionally, he was considered the last emperor of the Sui dynasty because he was succeeded and executed by Li Yuan (Emperor Gaozu of Tang), the founding emperor of the Tang dynasty. However, after him, his brother Yang Tong claimed the throne and continued to do so until 619. Li had rebelled against the rule of Yang You's grandfather Emperor Yang of Sui in 617 and captured the capital Chang'an later that year, seizing Yang You and installing Yang as a puppet emperor. However, only the commanderies under Li's control recognized Yang You as emperor. The rest of the commanderies continued to recognize Emperor Yang of Sui as emperor. In 618, after news arrived that Emperor Yang had been killed by the general Yuwen Huaji, Li had the young emperor yield the throne to him. Li then murdered and executed Yang You a year later. During Emperor Yang's reign Yang You was born in 605, as a son of Yang Zhao, the son and crown prince of Emperor Yang. His mother was Yang Zhao's wife, Crown Princess Wei. He was probably the youngest of Yang Zhao's three sons—he was clearly younger than Yang Tan (), born in 603, and probably younger than Yang Tong, whose birth year is unknown, based the order in which they were eventually created imperial princes. However, under Confucian principles of succession, he would have been considered Yang Zhao's proper heir, as his mother was Yang Zhao's wife, while Yang Tan's and Yang Tong's mothers were concubines. Yang Zhao died in 606. However, Emperor Yang did not make Yang You or either of his brothers crown prince to replace Yang Zhao, leaving matters ambiguous as to whether one of them, or Yang Zhao's younger brother Yang Jian the Prince of Qi, would inherit the throne eventually. He made the three sons of Yang Zhao imperial princes, and Yang You received the title of Prince of Dai. As Emperor Yang did not often stay in the capital Chang'an, starting 613, he made the eight-year-old Yang You nominally in charge of Chang'an, although he