Chén Zhènsūn 陳振孫 (ca. 1183–after 1249, conventionally 1183–1262), zì Bóyù 伯玉, hào Zhízhāi 直齋, was a Southern Sòng official and the greatest private book collector of his age, of Ānjí 安吉 (Húzhōu, Zhèjiāng). He served as a sub-prefectural and prefectural administrator in Zhèjiāng (1234–36 in particular as Zhèxī tíjǔ 浙西提舉), changed prefects to Jiāxīng 嘉興, and finally rose to shìláng 侍郞 (vice-minister) — Lì È’s 厲鶚 Sòngshī jìshì 宋詩紀事 understated his career as ending only at tíjǔ; Zhōu Mì’s 周密 Guǐxīn zázhì 癸辛雜識 corrects this, noting both that he served at shìláng and that his eldest son Chén Zhōushì 陳周士 was already known as the son of “Zhízhāi shìláng”. His Húzhōu library, accumulated by recopying the famous Pútián 莆田 collections of the Zhèng (Jiājì 夾漈), Fāng, Lín, and Wú families, exceeded 51,180 juan in 3,096 titles — by Sòng standards immense. The Zhízhāi shūlù jiětí KR2n0005 is his catalogue of this collection. CBDB 47935 places him from 1183 with floruit 1249; standard reference works (Wilkinson; Hervouet, A Sung Bibliography) give “ca. 1183 – after 1249”, and the conventional later figure 1262 is sometimes cited.