A textbook on the program of the course "Hydraulics" for students of mechanical engineering and mechanical specialties of higher technical educational institutions of Russia is designed to lay the foundation for design training of specialists in the field of hydraulic machines and hydraulic drives. Theoretical bases of calculation and design of hydraulic systems, units and parts of hydraulic drive are described. It contains information about liquids and their properties, as well as about hydraulic machines, the features of their design, operation, conditions of use and operation.