Zhāng yǐn jū 張隱居 (“Recluse Zhāng”) was a mid-Táng Daoist alchemist, author of KR5c0285 Zhāng zhēn rén jīn shí líng shā lùn 張眞人金石靈砂論 (composed 742–770, during the Tiān bǎo / Dà lì reigns of Táng Xuán zōng / Dé zōng). His personal name is lost; “yǐn jū” is a recluse-title. The work belongs to mid-Táng jīn shí 金石 (metals-and-minerals) alchemy.