A hydraulic actuator (1) is disclosed comprising a cylinder housing (2), a piston (5) with a piston rod (6) being displaceably arranged inside the cylinder housing (2) and a pressure amplifier (17) comprising an inlet section (18) with a pressure inlet port (20), an active section (19) with a high pressure outlet port (22), a low pressure chamber (32) and a high pressure chamber (38a). It is an objective of the invention to provide a hydraulic actuator (1) with a modular pressure amplifier (17). To this end, the hydraulic actuator (1) comprises a cartridge pressure amplifier (10) comprising a sleeve (10a) being arranged at least partially inside the piston rod (6), and wherein the pressure amplifier (17) is stationarily arranged inside the sleeve (10a).