The diaries of M. M. Bogoslovsky (1867–1929), one of the most prominent representatives of the Moscow school of historians, student and successor of V. O. Klyuchevsky at the departments of Russian history at Moscow University and the Theological Academy, are published in full for the first time. The basis consists of daily entries from July 1915 to November 1917; the surviving fragmentary entries of 1913 and a diary for two months of 1919 are also published. Numerous information about events and persons with whom M. M. Bogoslovsky encountered fate, the desire to write his observations in the context of Russian history make his diaries a valuable historical source, important for understanding the university and intellectual environment in an era of crisis of all traditional values. Diary entries also allow us to better understand the inner world of a major scientist, his worldview, evaluate his contribution to historical science and at the same time feel the charm of his personal, human qualities. For historians and everyone interested in Russian history.