The monograph is devoted to an important fundamental problem of plasma physics - the reconnection of magnetic power lines, or "magnetic reconnection", which initiates non-stationary high-energy phenomena in both space and laboratory conditions. Within the framework of the magnetohydrodynamic approach, theoretical aspects and applications of magnetic reconnection. are outlined. The basic concepts and processes inherent in magnetic reconnection are consistently considered - the formation of current layers during collapse at the zero point of X-type, a global three-dimensional magnetic topology with special power lines, various modes and types of reconnection, and so on. d. The role of magnetic reconnection in the interpretation of observations and the construction of models of various phenomena on the Sun and in the Earth's magnetosphere is considered, in the acceleration of charged particles. The results of targeted laboratory experiments on the study of magnetic reconnection. For researchers, specialists in plasma physics, magnetic hydrodynamics, astrophysics, solar physics and geophysics, students and graduate students of relevant specialties .