Abstract
The article thoroughly studies the stages of the theory of separation of powers formation. The concept of separation of powers has a long historical path and is the main component of a democratic state in the modern world. A great contribution to the development of the concept of separation of powers was made by Marsilius of Padua, who in the 14th century in his work «Defender of Peace» formulated the foundations of this concept. This work was one of the first theoretical studies of the concept of separation of powers. A major step in the study of this issue was made in the Age of Enlightenment. It is known that the socio-economic and cultural achievements of the Enlightenment required a new political system of the state, a new power system that would correspond to that time. That is why philosophers paid attention to this issue at that exact time. It is believed that the basis for the theory of separation of powers emergence was mainly the ideas of J. Locke, and S. Montesquieu, it is they who formulated the fundamental principles of the theory of separation of powers.