Cao Rui () (204 or 205 – 22 January 239), courtesy name Yuanzhong, was the second emperor of the state of Cao Wei during the Three Kingdoms period. His parentage is in dispute: his mother, Lady Zhen, was Yuan Xi's wife, but she later remarried Cao Pi, the first ruler of Wei. Based on conflicting accounts of his age, Pei Songzhi calculated that, in order to be Cao Pi's son, Cao Rui could not have been 36 (by East Asian age reckoning) when he died as recorded, so the recorded age was in error; late-Qing scholars Lu Bi (卢弼) and Mao Guangsheng (冒广生) argued instead that Cao Rui was Yuan Xi's son.
Cao Rui's reign was viewed in many different ways throughout Chinese history. He devoted many resources into building palaces and ancestral temples, and his reign saw the stalemate between his empire, Shu Han, and Eastern Wu become more entrenched. His building projects and his desire to have many concubines (who numbered in the thousands) greatly exhausted the imperial treasury.
