Western-Hàn court eunuch and educator, active under Hàn Yuándì (r. 49–33 BCE). Held the post of Huángmén lìng 黃門令 (subordinate to the Shàofǔ, supervisor of palace inner-staff). His sole surviving work, the Jíjiù piān KR1j0017, is the earliest extant Chinese children’s primer and the source — by tradition reported in Zhāng Huáiguàn’s Shūduàn — of the zhāngcǎo 章草 cursive script: Shǐ Yóu first wrote out the Jíjiù in a loosened clerical-script that became the model for the later zhāngcǎo tradition. Beyond his composition of the Jíjiù, no biographical data are recoverable; the Hànshū gives him no separate biography, and the Yìwénzhì mentions him only in the closing summary of the Xiǎoxué class.