Xú Zǐguāng 徐子光 (fl. 12th c.) was a Northern–Southern Sòng commentator known only for his Méngqiú jízhù 蒙求集註 (KR3k0010), the Collected Notes on Lǐ Hàn’s foundational rhymed primer of historical gùshí. Chén Zhènsūn’s Zhízhāi shūlù jiětí records the commentary in 8 juan; later editions consolidated it to 2 juan. No biographical material on Xú survives in the Sòng shǐ or in bǐjì literature; his native place and offices are unknown. The Sìkù tíyào critiques several specific slips in his notes — citing Zhū Yì’s Yījué liáo zájì — but concludes that overall the work is broadly conversant and serves as a “ferry-raft for beginners”.