Prathamāchāryan — The First and Primordial Āchārya
Prathamāchāryan ('the first Āchārya') is the title given to Śrīman Nārāyaṇa Himself in the Śrī Vaiṣṇava tradition, recognising Him as the original teacher (ādi guru) from whom all knowledge, the Veda, and the Āchārya lineage ultimately flow.
Basis in Scripture: The Bhagavad Gītā (4.1) reveals that Bhagavān first taught this eternal yoga to Vivasvān (the Sun-god), who taught it to Manu, who taught it to Ikṣvāku — establishing the divine guru-paramparā. Bhagavān is thus the prathamāchāryan — the teacher without a teacher above Him.
In Śrī Vaiṣṇava Paramparā: The guruparamparā begins: Śrīman Nārāyaṇa → Lakṣmī (Śrī) → Viṣvaksena → Nammāzhvār → Nāthamuni → Yāmunāchārya → Śrī Rāmānujāchārya... Śrīman Nārāyaṇa is the prathamāchāryan of this entire chain.
Devotional Significance: Recognising Bhagavān as prathamāchāryan places the Āchārya-disciple relationship in a cosmic frame — one's own Āchārya is the latest link in a chain that begins with Bhagavān Himself. This deepens the disciple's reverence for the human Āchārya, who carries the transmission of divine knowledge.