Yáo Xìn 姚信 (fl. mid 3rd century), zì Yuánzhí 元直, was a SūnWú 孫吳 classicist and astronomer, a native of Wúxīng 吳興 (the Kanripo title-list places him under Shǔ, but the Suí shū jīngjí zhì and the early bibliographic tradition place him under Wú; the dynasty here follows the Suí shū). He served at the Wú court as Cavalier Attendant-in-Ordinary (太常卿) under Sūn Hào 孫皓. His birth and death years are not preserved; he is conventionally placed in the mid 3rd century. CBDB has no entry.
He is best known for two works: a Zhōu Yì zhù 周易注 — Wú-period Yì commentary that survives in fragments preserved in Lǐ Dǐngzuò’s 李鼎祚 Táng-period Zhōu Yì jí jiě 周易集解, and the Shìwěi 士緯 — a rénwù (personnel evaluation) treatise. The Suí shū jīngjí zhì lists the Shìwěi in 10 juàn.
In the Kanripo corpus he is the attributed author of KR3a0148 Shìwěi 士緯.