Gao Yun (Chinese: 高雲) (died 409), at one time Murong Yun (慕容雲), courtesy name Ziyu (子雨), also known by his posthumous name as the Emperor Huiyi of Later/Northern Yan (後/北燕惠懿帝), was either the last monarch of China's Later Yan dynasty or the founding monarch of China's Northern Yan dynasty, depending on the historian's characterization.
He was a descendant of the royal house of Goguryeo (Gaogouli), whose ancestors were captured by the Former Yan dynasty.
In 409, he was assassinated, and after a disturbance, was replaced by his ethnic Han general Feng Ba (Emperor Wencheng).
When Murong Huang defeated Goguryeo forces and temporarily occupied its capital Hwando, he took many members of the Goguryeo royal house captive and moved them to Qingshan (青山, in modern Jinzhou, Liaoning), and their descendants became Former Yan and Later Yan subjects.
As of 397, Gao Yun was a mid-level official in the administration of Murong Bao (Emperor Huimin), when Murong Bao, under military pressure by Northern Wei, abandoned the capital Zhongshan (中山, in modern Baoding, Hebei) and sought to take refuge at the old Former Yan capital of Longcheng (龍城, also in Jinzhou).
Eventually, Murong Xi accompanied Empress Fu's funeral procession out of Longcheng.
Murong Xi returned to Longcheng and settled in outside his estate of Longteng Chateau (龍騰苑), preparing an assault on the city.
Being insecure about how he felt he had little contributions to the people or to his own place on the throne, he employed many skillful guards to protect him.
Feng Ba, upon hearing of the assassination, readied his troops and waited for the situation to become clear, but two of his soldiers, Zhang Tai (張泰) and Li Sang (李桑), advanced into the palace and beheaded Li and Tao.