The essay What is Sanskrit was published in 1911 as a preface to P. Ritter’s Sanskrit textbook. It is an updated version of the trial lecture, given by him in the fall of 1899 at Kharkiv University (Ukraine). There he was teaching Sanskrit from the autumn of 1900 at the Department of Comparative Linguistics and headed this Department later. The author debunks popular myths about Sanskrit, describes its place among Indian languages emphasizing temporal and geographical differences between Sanskrit and Vedic language, distinguishes epic and classical Sanskrit, lists the prominent works of Sanskrit literature, and pays tribute to the Indian grammatical tradition. He mentions such prominent works of ancient Indian Sanskritology as the Aṣṭādhyāyī of Pāṇini (4th–3rd centuries BC), Nirukta of Yāska (4th century BC), Vārttika of Кātyāyana (3rd–2nd centuries BC), Mahābhāṣya of Patañjali (2nd century BC). Ritter’s account of the history of the discovery and study of Sanskrit in the West is interesting, as is the characterization of Sanskrit scholars (his predecessors and contemporaries), some of whom he knew personally. Ritter’s students testified that he was fluent in Ukrainian which he apparently knew from childhood but the lecture was given by him and then published in Russian as a result of two hundred years of systematic extirpation of the Ukrainian language in the Russian Empire. All notes except two marked are written by the translator. The notes provide philological, historical, and biographical information. The introductory article tells about the origin of P. Ritter, his studies, his work as a scientist, translator, compiler of the Ukrainian-language Anthology of Ancient Indian Literature, lecturer, and organizer of science, as well as about his hobby and his tragic death due to repressions of NKVD (People’s Commissariat for Internal Affairs).