Emperor Kang of Jin (simplified Chinese: 晋康帝; traditional Chinese: 晉康帝; pinyin: Jìn Kāng Dì; Wade–Giles: Chin K'ang-ti; 322 – 17 November 344), personal name Sima Yue (司馬岳), courtesy name Shitong (世同), was an emperor of the Eastern Jin Dynasty (265-420). He was a son of Emperor Ming and younger brother (by the same mother) of Emperor Cheng. His reign was brief—only two years.

Sima Yue was born in 322 as the second son of Emperor Ming, by his wife Empress Yu Wenjun. After his father died in 325 and was succeeded by his brother Emperor Cheng, Sima Yue was created the Prince of Wu in 326. In 327, because his uncle Sima Yu the Prince of Langye wanted to yield that more honorific title, Sima Yu was created the Prince of Kuaiji and Sima Yue was created the Prince of Langye. It is not known where Sima Yue was during the Su Jun Disturbance of 326–328—whether he was captured and held hostage like his emperor brother, at his principality of Wu (which Su Jun did not occupy), or elsewhere. During his brother's reign, he received a progression of offices, but did not appear to actually participate in major decision-making.

In summer 342, Emperor Cheng grew gravely ill. He had two young sons -- Sima Pi and Sima Yi, then still in cradles, by his concubine Consort Zhou. Yu Bing (庾冰), one of the top two officials and Emperor Cheng's (and Sima Yue's) uncle, fearful that the Yus would lose power if a young emperor were named, persuaded Emperor Cheng that in the face of the powerful enemy Later Zhao that an older emperor should be named. Emperor Cheng agreed and designated Sima Yue the Prince of Langye, despite the other top official He Chong (何充)'s opposition. He died soon after, and Sima Yue took the throne as Emperor Kang. (He did not make secret his opposition, and after Emperor Kang took the throne, when he thanked Yu and He for making him emperor, He stated, "The reason why Your Imperial Majesty can fly like a dragon is Yu Bing. If I were listened to, we would not have this current prosperous reign." Emperor Kang appeared humiliated, but did not retaliate against He (although He himself would request to become a local governor to avoid working with Yu Bing, and his request was granted) and continued to respect him.)

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