The Yiyuan 異苑 "Garden of the extraordinary" is a collection of phantastic stories compiled by the Liu-Song period 劉宋 (420-479) writer Liu Jingshu 劉敬叔 (fl. 417-426), who came from Pengcheng 彭城 (modern Xuzhou 徐州, Jiangsu) and was adjutant of the Inner Troops (zhongbing canjun 中兵參軍), adjutant of general Liu Daolian 劉道憐，and finally chamberlain for attendants (langzhongling 郎中令) of general Liu Yi 劉毅. Only 10 juan "scrolls" of the original Yiyuan have survived, but is can be assumed that not much is lost.
The book includes 382 stories of strange events and supernatural appearings from ancient times until the Jin period 晉 (265-420), the latter covering the largest part of the stories.
The literary quality of the stories differs widely. While most of them are written in a very simple and coarse language, others are more refined, like Zigushen 紫姑神 or Zhang Shen 章沉. Part of the stories was later used and expanded, especially by Tang period 唐 (618-907) writers. Wen Jiao's 溫嶠 story Niuchu ran xi 牛渚燃犀 "Burning the rhino horn of Mt. Niuchu", for instance, or some poems of Du Fu 杜甫 use the story Tao Kan Hunu 陶侃胡奴 "Tao Kan and his son Hunu" that is part of the Yiyuan. Some stories, like that of Zhang Hua 張華, are written on an historical background but transgress the border to fiction, and others wholly belong to the realm of phantasy, like the story of the parrots dousing the forest fire.
The original book is lost, and the received text is a collection of fragments quoted in Song period 宋 (960-1279) encyclopedias like Taiping yulan 太平御覽, Taiping guangji 太平廣記 and Shilei fu zhu 事類賦注.
The Yiyuan is included in the reprint series Tang-Song congshu 唐宋叢書, Wuchao xiaoshuo 五朝小說, Mice huihan 秘冊彙函, Jindai mishu 津逮秘書, Xuejin taoyuan 學津討原, and Siku quanshu 四庫全書.
Bai Huawen 白化文 (1986). "Yiyuan 異苑", in: Zhongguo da baike quanshu 中國大百科全書, Zhongguo wenxue 中國文學, vol. 2, pp. 1167-1168. Beijing/Shanghai: Zhongguo da baike quanshu chubanshe.
Li Xueqin 李學勤, Lü Wenyu 呂文鬰 (1996). Siku da cidian 四庫大辭典, vol. 2, p. 2172. Changchun: Jilin daxue chubanshe.