P. S. Subrahmanya Sastri (29 July 1890 – 20 May 1978) was a Sanskrit scholar, who also acquired mastery over Tamil language and literature.

He also learnt Nyaya (logic) and Alankara Sastra (Poetics and Literary Criticism) from Prof. S. Kuppuswami Sastri of the Madras Presidency College (professor of Sanskrit and comparative philology, and curator of the Government Oriental Manuscripts Library, Madras[2]) and Mimamsa (Linguistics) from Chinnaswami Sastri of the Benares Hindu University.

All these inspired Subrahmanya Sastri to take up a systematic study of Tamil literature and grammar.

Subrahmanya Sastri's text on Tolkappiyam in Roman transliteration and English translation received encomiums from linguists across the world.

On his retirement, he returned to Thiruvaiyaru and completed the translation of the Mahabhashya into English (in 14 volumes running to about 4,000 pages) on the advice of the Mahaperiyava of Kanchi.

Under each sutra just before taking up the bhashya, Subrahmanya Sastri had pointed out the topics that would be dealt with in the great commentary.

With a view to elucidating the obscure points, he often added notes mostly based on Kaiyata's Pradipa and Nagesabhatta's Udyota.

Apart from his mastery over Sanskrit, Tamil and English, he also studied German, French, Telugu, Kannada and Malayalam.

Subrahmanya Sastri, who was known for his simplicity, taught Tirukkural to a manual scavenger during his retired life at Tiruvaiyaru.