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 Lǚ-Jìtāng 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 Lǚ-Jìtāng 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.