The purpose of the article is to briefly highlight the main milestones in the life of the famous Buryat scientist P. B. Baldanzhapov, to characterize his scientific researches in the field of Mongolian studies, to discover new, little-known aspects of his activities, to show his role in the development of new fields of science. Introduction. The article was presented as an introductory report at the IV International seminar “Written Heritage and current problems of the history and culture of the Mongolian peoples”, dedicated to the 100th anniversary of the birth of the prominent Russian scientist, Mongolist and orientalist P. B. Baldanzhapov (1921–1991), held in Ulan-Ude on September 16–18, 2021. The source base was both published works and unpublished materials stored in the personal archive of the scientist, articles by researchers dedicated to the legacy of P. B. Baldanzhapov. When writing the article, general historical research methods were used, such as historical-comparative, retrospective and chronological, which made it possible to show the life and works of P. B. Baldanzhapov in the process of becoming from a student to a professional. Results. Professional interests of P. B. Baldanzhapov were quite versatile: from collecting and studying monuments of folk folklore, toponymic terms and their interpretation, collecting written monuments in Tibetan and Mongolian languages, what is evidenced by the unique collections of Tibetan and Mongolian works stored in his personal archive, numerous manuscripts of articles and materials on the history of public education, culture, science and librarianship in Mongolia and Tuva, on the history of preserving cultural heritage and organizing their museum display and popularization deposited in his archive, up to studying the Buddhist heritage and promoting its preservation, as well as sources on Indo-Tibetan medicine and many others. Nevertheless, the main passion of his whole life was the study of Mongolian historical treatises.