In the article, the biography of Blessed Father Klymentiy (Casimir) Count Sheptytsky (1869-1951) has been reconstructed in the “reference-encyclopedic” version on the basis of the achievements of diasporic and contemporary domestic historiography. Given the historiographical disproportions in the coverage of his biography, which has been reflected in relatively little attention to the early period of life and the creation of new “myths”, the periodization of main stages (milestones) of life and consistent reconstruction of biography of Casimir / Klymentiy Sheptytsky have been conducted. His family environment, education, worldview formation and evolution have been described, the peculiarities of his social and political activity in the regional societies and the Austrian parliament have been shown, the motives and circumstances of the choice of monastic life have been clarified. The activity of Klymentiy Sheptytsky on the revival and development of Studite monasticism in Galicia, support of Andrey Sheptytsky’s initiatives on the development of the Greek Catholic Church in different state-political regimes (Austria-Hungary, ZUNR, the Second Commonwealth, the first Soviet occupation, German occupation and formation of the USSR) and the spread of its influence outside Galicia, in the east, have been analyzed. The tragic page of the last years of Klymentiy Sheptytsky’s life from arrest and exile to death has been covered. A number of “unresolved” issues in his biography that require the search for new sources and more detailed scientific studies have been identified, including the cheirotonia of a bishop.