Zhào Yànsù 趙彥肅 (fl. late twelfth century, probably c. 1140s–c. 1195/96), zì Zǐqīn 子欽, hào Fùzhāi 復齋. A member of the Sòng imperial clan (zōngshì 宗室). Jìnshì (year not specified in the tiyao); held a sequence of relatively junior provincial posts under Xiàozōng and the early reign of Guāngzōng / Níngzōng: Shūjì 書記 (Bookkeeper) at Níngguójūn 寧國軍, Tuīguān 推官 (Recommendation-Officer) of Xiùzhōu 秀州, Xiànchéng 縣丞 (Deputy Magistrate) of Huátíng 華亭 with provisional charge of the magistracy. Returned home for inner-mourning (nèijiān 內艱).
A protégé of Zhū Xī. Zhū Xī recommended him to the chief minister Zhào Rǔyú 趙汝愚 (1140–1196); Rǔyú then memorialized for his appointment as jiédù tuīguān 節度推官 of Nínghǎijūn 寧海軍, but Zhào Yànsù fell ill almost immediately upon assumption and died — placing his death plausibly in Qìngyuán 1 or 2 (1195/1196), just before or at the onset of the Qìngyuán dǎngjìn 慶元黨禁 (“False Learning Proscription”).
Zhū Xī praised his Guǎng záxué biàn 廣雜學辨 (an extension of Zhū Xī’s own Záxué biàn), his Shìguānlǐ 士冠禮, Hūnlǐ 婚禮, and Kuìshí lǐtú 饋食禮圖 (ritual diagrams). The one substantive disagreement was over the Yì: Zhū Xī’s Yǔlèi records the verdict that Zhào Yànsù’s Yì-exposition is “too refined, too tight, sometimes injuring the jiǎnyì (easy-and-simple) flavor.”
Within the Kanripo corpus he is the author of KR1a0036 Fùzhāi Yì shuō 復齋易說. CBDB id 50806 records the imperial-clan affiliation but lacks lifedates, consistent with the sparse biographical apparatus.