In this study, the development of a novel hydraulic robotic actuator is introduced. With the use of additive manufacturing (AM), lightweight and compact design can be achieved. A high load-to-weight ratio 3-DOF robot actuator with orthogonally connected hydraulic rotary cylinders is designed for AM. To validate the feasibility, a titanium hydraulic robot actuator is prototyped by using the metal powder bed fusion (M-PBF) AM process. A set of loading experiments are conducted on the AM-printed prototype. The study shows that system-level AM design and manufacturing methods can help gain increased output torque but with reduced weight and volume. With the use of hydraulic driving, the robotic actuator is more compact and solid to resist to tough environments as compared with the traditional actuators using electric motors. This study also implies the potential wide application of AM to design and print similar hydraulic link mechanism in heavy-duty robot or mobile humanoid robot.