Xú Yànchún 徐彥純 (zì Yòngchéng 用誠, d. c. 1384), native of Yìwū 義烏 (modern Zhèjiāng), was a late-Yuán / early-Míng physician and one of the principal direct disciples of Zhū Zhènhēng 朱震亨 (1281–1358) in the Dānxī 丹溪 school. After Zhū’s death he carried on the tradition through the LǚJìtāng 履義堂 academy in Yìwū and produced two key syntheses: the Yī xué jí yùn 醫學集驗 (verified knowledge in medicine) and the Běncǎo fāhuī 本草發揮 (KR3ec012). His likely death date 1384 (洪武十七年) is inferred from the dating of his LǚJìtāng activities, not directly attested.
No confident CBDB id. He is one of the principal conduits through which Zhū Zhènhēng’s pharmacology entered the Míng canon; Lǐ Shízhēn’s 李時珍 Gāngmù 丹溪云 citations are mostly second-hand through Xú.