Hydraulic machine are those machines which convert hydraulic energy (energy possessed by water) into mechanical energy (which is further converted into electrical energy) or mechanical energy into hydraulic energy. The hydraulic machines, which convert the hydraulic energy into mechanical energy, are called turbine while the hydraulic machines which convert the mechanical energy into hydraulic energy are called pumps.

This machinery and tools that use liquid fluid power to do simple work, operated by the use of hydraulics, where a liquid is the powering medium. In heavy equipment and other types of machine, hydraulic fluid is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders and becomes pressurised according to the resistance present.

The fluid is controlled directly or automatically by control valves and distributed through hoses and tubes.The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and wide array of actuators that can make use of this power, and the huge multiplication of forces that can be achieved by applying pressures over relatively large areas.