Liu Xin (; c. 50 BC – AD 23), courtesy name Zijun , was a Chinese astronomer, historian, and editor during the Western Han Dynasty (206 BC-AD 9) and Xin Dynasty (AD 9–23). He later changed his name to Liu Xiu due to the naming taboo of Emperor Ai of Han. He was the son of Confucian scholar Liu Xiang (77–6 BC) and an associate of other prominent thinkers such as the philosopher Huan Tan (d. 28 AD). Liu founded the Old Text school of Confucianism.