Héngyuè zhēnzǐ 衡嶽真子 (“Perfected Master of Mount Héng”) is the Daoist pseudonym of a tenth-century commentator from the southern sacred-mountain tradition (Mount Héng / Nányuè 南嶽 in present-day Húnán). He is named in the Daoist canon as the zhù 註 (annotator) of one of the two parallel commentaries on the Xuánzhū xīnjìng 玄珠心鏡 corpus, transmitted in the Daozang as KR5b0279; he draws extensively on the Lǎojūn xīshēng jīng 老君西昇經 and the Lǎojūn nèiguān jīng 老君內觀經 as scriptural foundations for the doctrine of the yīzhī yuán 一之元 (the source of the One). The companion commentary at KR5b0280 is by the Táng-period figure 王損之 (棲真子) transmitting the work of 長孫滋. No CBDB record is locatable; the figure is known only by his pseudonym.