Sachchidananda Hirananda Vatsyayan (7 March 1911 – 4 April 1987), popularly known by his nom de plume Agyeya (lit.
Unknowable), was an Indian writer, poet, novelist, literary critic, journalist, translator and revolutionary in Hindi language.
He is regarded as the pioneer of the Nayi Kavita (New Poetry) and Prayogavaad (Experimentalism) movements in modern Hindi literature.
He also edited the Saptaks, a poetry series, and started the Hindi newsweekly Dinaman.Agyeya translated some of his own works, as well as works of some other Indian authors to English.
He also translated some books of world literature into Hindi.