A novel direction of arrival (DOA) estimation system based on a broadband 3D printed Luneburg lens is reported in this paper. Using the property of a Luneburg lens that the focus point of an incident plane wave is at the opposite side on the surface of the lens, 36 diode detectors with 10 degree spacing are mounted around the surface of a 3D printed Luneburg lens to estimate the DOA of a microwave signal in the azimuth plane (full 360 degrees coverage). A correlation algorithm is used to estimate the angle of the incoming signal.