Emperor Hui of Jin, (259-poisoned January 8, 307), personal name Sima Zhong, courtesy name Zhengdu, is the second emperor of the Jin Dynasty (265-420).

Emperor Hui is a developmentally disabled ruler, and throughout his reign, there is constant internecine fighting between regents, imperial princes (his uncles and cousins), and his wife Empress Jia Nanfeng for the right to control him (and therefore the imperial administration), causing great suffering for the people and greatly undermining the stability of the Jin regime, eventually leading to the Wu Hu rebellions that lead to Jin's loss of northern and central China and the establishment of the competing Sixteen Kingdoms.

He is briefly deposed by his granduncle Sima Lun, who usurps the throne himself, in 301, but later that year is restored to the throne and continues to be the emperor until 307, when he is poisoned, likely by the regent Sima Yue.