Zhào Shuǎng 趙爽 (also given as 趙嬰, zì Jūnqīng 君卿; fl. early 3rd century, Wú 吳 of the Three Kingdoms) is the author of the principal Hàn-Three Kingdoms commentary on the Zhōubì suànjīng 周髀算經 (KR3fa002, KR3f0001). His zhù 注 and the appended Gōugǔ yuánfāng túshuō 句股圓方圖說 (“Discourse on the Diagrams of Square and Circle Constructed from gōu and gǔ”) preserve the earliest surviving geometric demonstration of the right-triangle relation gōu²+gǔ²=xián² in any Chinese source — the famous “xián tú 弦圖” diagram that became the emblem of pre-modern Chinese mathematics (it was the logo of the 2002 ICM in Beijing). Almost nothing else is recorded of his life; the standard biographical scaffolding rests on the dedicatory note of his own commentary and on later citations in 李淳風’s Táng-imperial zhèngyì on the Ten Mathematical Classics.