Yi Yuanji (; Wade-Giles: I Yüan-chi; c. 1000, Changsha, Hunan – c. 1064) was a Northern Song dynasty painter, famous for his realistic paintings of animals. According to Robert van Gulik, Yi Yuanji's paintings of gibbons were particularly celebrated.Van Gulik, Robert Hans (1967), The gibbon in China: An essay in Chinese animal lore, E. J. Brill, Leiden, Holland. There is a brief summary at Thomas Geissmann, Gibbon paintings in China, Japan, and Korea: Historical distribution, production rate and context" . Gibbon Journal, No. 4, May 2008.

The 11th-century critic Guo Ruoxu () in his Overview of Painting (图画见闻志, Tuhua Jian Wen Zhi) says the following about Yi's career:English translation by Van Gulik, in Van Gulik (1967), p. 79

He spent months roaming the mountains of southern Hubei and northern Hunan, watching roebucks () and gibbons () in their natural environment.

In 1064, Yi Yuanji was invited to paint screens in the imperial palace. Once this job was completed, the Yingzong Emperor, impressed, commissioned him to paint the Picture of a Hundred Gibbons, but the artist died after painting only a few gibbons. A few of his other gibbon paintings have survived, and van Gulik, quite familiar with the behavior of this ape, comments on how natural they look in the paintings. His other work includes depictions of deer, peacocks, birds-and-flowers and fruits-and-vegetables; many of them are kept in the National Palace Museum in Taipei. The Monkey and Cats painting has been described as an outstanding example of playfulness and intimacy.MASTERPIECES OF CHINESE ART (archive link), Time Magazine, May 6, 1957 Van Gulik identifies the monkey as a macaque. This painting was featured on a 2004 "Year of the Monkey" stamp from Saint Vincent and the Grenadines.Feline Philately: Cats on stamps

The image of Yi Yuanji, with his intimate knowledge of nature, has attracted attention from modern Chinese painters.Painting by modern artist Fan Zeng (范曾) Yi Yuanji playing with a monkey (易元吉戏猴图)" , painting by the modern Chinese artist Fang Zeng (范曾)

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