Yang Tong (Chinese: 楊侗; 604–619), known in traditional histories by his princely title of Prince of Yue (越王) or by his era name as Lord Huangtai (皇泰主), posthumous name (as bestowed by Wang Shichong) Emperor Gong (恭皇帝), courtesy name Renjin (仁謹), was an emperor of the Chinese Sui Dynasty. During the disturbances that permeated throughout the Sui state late in the dynasty's history, his grandfather Emperor Yang left him in charge of the eastern capital Luoyang, and after Emperor Yang was killed by the general Yuwen Huaji in 618, the Sui officials in Luoyang declared Yang Tong emperor. However, soon one of those officials, Wang Shichong, seized power, and in 619 had Yang Tong yield the throne to him, ending Sui. Soon, he was killed on Wang's orders.

Yang Tong was born in 605. He was the second of three sons of Yang Zhao, Emperor Yang's son and crown prince. His mother was Yang Zhao's concubine, Consort Liu.

In 606, Yang Zhao died. According to Confucian principles of succession, Yang Tong's younger brother Yang You, also born in 605, would have been considered Yang Zhao's heir and successor, as Yang You was born of Yang Zhao's wife Crown Princess Wei. However, Emperor Yang did not create Yang You, Yang Tong, or their older brother Yang Tan (楊倓, born in 603) crown prince to replace Yang Zhao, but left the matters of succession ambiguous between them and Yang Zhao's younger brother Yang Jian the Prince of Qi. He did, however, create Yang Tong and his brothers imperial princes, and Yang Tong was created the Prince of Yue.

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