Nanchū 南忠 — Early Heian-period Japanese Shingon scholar-monk active in the mid-9th century. His one extant work, the Zhù Dàfódǐng zhēnyán 註大佛頂眞言 (KR6j0182, T61n2234), is dated by its own colophon to “summer of the 14th year of Jōwa” 承和十四年 = 847 CE, providing a firm anchor for his floruit.
In the preface to that work he names his teacher as Reverend Reigan 靈巖和尚, whom he describes as having “entered the great Tang to receive instruction in this dhāraṇī explanation” 入於巨唐請益此眞言釋 and as having brought back to Japan the corresponding ritual codification (儀軌). Nanchū himself received the dhāraṇī commentary from this teacher as part of his own 受法 dharma reception, and his commentary is explicitly produced under the teacher’s 印可 sanction, based on the Sanskrit (梵本) text supplied by Amoghavajra 不空. This places Nanchū in the second generation of the Heian Shingon scholastic transmission — that is, in the generation immediately after Kūkai’s direct disciples — and identifies his line of transmission as one of the multiple early-Heian routes through which the Tang Esoteric commentarial apparatus was naturalized in Japan.
Source: DILA Buddhist Person Authority A000816; the colophon and preface of the Zhù Dàfódǐng zhēnyán itself.