This essay introduces Dangyouji 澹游集, a poetry anthology compiled by the famous late Yuan-early Ming dynasty literary monk, Jianxin Laifu 見心來復 (1319-1391) from poems that were written for him by his diverse array of colleagues. Today a copy of this anthology is housed in the The Naikaku Bunko in Tokyo. The Naikaku Bunko copy of Dangyouji was printed by the Gozan press from blocks carved from the Yuan dynasty edition. The Dangyouji has preface by Liu Renben dated Zhizheng 24 (1364) which indicates that Jianxin compiled this anthology while he was head priest of the Dingshui-si temple in Cixi, Zhejiang province. The Naikaku Bunko copy of the Dangyouji is the only reported copy traditionally preserved and transmitted in Japan. Given that copies of the anthology disappeared in China at an early date, the Dangyouji was not included in such compilations as the Wenyuange edition of the Sikuquansyu 四庫全書 or the 1st, 2nd or 3rd editions of the Sibucongkan 四部叢刊. While the author has seen listings for the Dangyouji anthology in the late Ming-early Qing Qiangqingtangshumu 千頃堂書目 by Huan Yuji and in the Qing dynasty Airijinglucangshuzhi 愛日精盧藏書志 by Zhang Jingwu, the present location of the edition of the Dangyouji referred to in these Qing dynasty remarks is unknown. The Yuan dynasty biographical index,Yuanrenchuanjisuotin 元人傅記資料索引 by Wng Deyi, Li Rongcun, and Pan Baideng (Taipei, 1979) did not list Dangyouji among the pubulications noted. From these various indications it appears that the Naikaku Bunko copy printed in Japan is the only extant version of the book. Also, the Naikaku Bunko copy is a good replication of the original form of the book as it was published during the Yuan dynasty. The Naikaku Bunko version of the Dangyouji Consists of Liu Renben's preface and three chapters, recording a total of 221 poems and compositions by 148 figures who interacted with the editor, ranging from famous landowners to regional bureaucrats, school administrators, retired literati, and Buddhist and Daoist priests. Of the three chapters, the first two contain the poems addressed to Jianxin, while chapter 3 records the texts of colophons and dedicatory inscriptions on monuments. The three chapters also include some of Janxin's own poetry and commentary. The anthology provides biographical information about each of the authors published, including surname, personal names, birthplace and official rank. This will stand as an important contemporary reference source for research in this field, complementing the information found in the Yuanrenchuanjisuotin. When several poems by a single author are listed, they are arranged in chronological order, proof of Jianxin's meticulous editing of the volume. Authors of poems collected in the Dangyouji include such famous landowners as Yu Ji 虞集, Jie Xisi 揭傒斯 and Ouyang Xuan 歐陽玄, and members of Jade Mountain such as Gu Ying 顧瑛, thus indicating that many of the major literary figures of the late Yuan dynasty are represented in the volume. This makes the Dangyouji a valuable tool for those researching the literary history of this period. In addition to the analysis of the contents and organization of the Dangyouji, this article includes a brief chronology of Jianxin's activities which clarifies previously unknown elements of the first half of Jianxin's life.