|This article does not cite any sources. (December 2009) (Learn how and when to remove this template message)|
|Crown Prince of Jin Dynasty|
|Successor||Sima Zang (imperial grandson)|
|Died||300 (aged 21–22)|
|Issue||Sima Bin, Prince of Nanyang
Sima Zang, Prince Ai of Muyang
Sima Shang, Crown Prince Huaichong
|Father||Emperor Hui of Jin|
|This article is part of
the War of the Eight Princes
|Other key figures|
|Empress Yang Zhi|
Sima Yu's father Sima Zhong was developmentally disabled, and before he, then crown prince, was to marry his wife Jia Nanfeng, his father Emperor Wu gave him one of his own concubines, Consort Xie Jiu (謝玖), so that Consort Xie could teach him how to have sexual relations. While Crown Princess Jia bore the crown prince four daughters, Sima Yu was his only son.
When Sima Yu was four years old, there was a fire in the palace, and Emperor Wu walked up a tower to observe it. Sima Yu pulled him aside and said, "At night, when something unusual like this happens, we should take precautions. The light of the fire should not shine on the emperor." Emperor Wu was surprised by this perceptive observation by a child, and praised the young prince as very much like his own grandfather Sima Yi. This was part of the reason why Emperor Wu let Crown Prince Zhong remain his heir. In 289, he created Prince Yu the Prince of Guangling. After Emperor Wu died in 290, Crown Prince Zhong ascended the throne as Emperor Hui, and Prince Yu was created crown prince.
As Crown Prince Yu grew in age, however, he lost some of the good reputation that he had as a child, as he disliked studying and spent much time on building projects and games. Empress Jia, who had constantly been jealous of Crown Prince Yu and Consort Xie, did not discourage this behavior, but in fact encouraged it to further damage Crown Prince Yu's reputation. When Crown Prince Yu's staff would try to correct his ways, he would not listen to them. He also would not listen to them with regard to their advice to maintain strong relations with Empress Jia's family members. Empress Jia's mother Guo Huai (郭槐) had constantly advised Empress Jia to treat Crown Prince Yu well, as her own son, and she advocated marrying a daughter of Empress Jia's sister Jia Wu (賈午) to Crown Prince Yu. However, Empress Jia and Jia Wu opposed this, and instead married a daughter of the official Wang Yan (王衍) to Crown Prince Yu. (Wang had two daughters, but Empress Jia had Crown Prince Yu marry the less beautiful one and had her nephew Jia Mi marry the more beautiful one.) After Lady Guo's death, the relationship between Empress Jia and Crown Prince Yu quickly deteriorated, as Jia Wu and another associate of Empress Jia, Emperor Wu's concubine Consort Zhao Can (趙粲), provoked difficulties between them. Further, Crown Prince Yu and Jia Mi never liked each other, and Jia Mi, as a result, also advised Empress Jia to depose Crown Prince Yu.
In 299, Empress Jia agreed and took action. When Crown Prince Yu was in the palace to make an official petition to have his ill son Sima Bin (司馬彬) created a prince, Empress Jia forced him to drink a large amount of wine and, once he was drunk, had him write out a statement in which he declared intention to murder the emperor and the empress and to take over as emperor. Empress Jia presented the writing to the officials and initially wanted Crown Prince Yu executed—but after some resistance, she only had him deposed and reduced to status of a commoner. Crown Prince Yu's mother Consort Xie was executed, as was his favorite concubine Consort Jiang Jun (蔣俊, Sima Bin's mother). Wang Yan divorced his daughter from the crown prince, who wrote an extant, lengthy letter to her explaining the incident through which Empress Jia framed him.
In 300, under the advice of a prince she favored -- Sima Lun the Prince of Zhao, Emperor Wu's granduncle—Empress Jia decided to eliminate Crown Prince Yu as a threat. She sent assassins and had Crown Prince Yu assassinated. He was buried with honors due a prince—under the title of Prince of Guanling. Sima Lun's intent was, however, to use this assassination as excuse to overthrow Empress Jia, and he did so later that year. He had Crown Prince Yu reburied with the honors due a crown prince and had him given the posthumous name Minhuai. He also welcomed Crown Princess Wang back to the palace, along with Crown Prince Yu's surviving sons Sima Zang (司馬臧) (whom he had created crown prince) and Sima Shang (司馬尚). However, when Sima Lun then usurped the throne briefly in 301, Crown Prince Zang was killed. After Emperor Hui's restoration later that year, Sima Shang was created crown prince, but died in 302, extinguishing Crown Prince Yu's line.