In this article, a novel class of self-packaged wideband bandpass power divider (PD) with constant power dividing ratio (PDR) and full range of 0 ° ∼ 360 ° arbitrary phase difference is presented for the first time. The proposed topology is constructed by reference and main paths, where each branch mainly consists of a transmission line (TL) section, open-ended stepped-impedance stubs, symmetrical open-ended CL sections, and a gray box. By properly selecting the circuit type of the gray box of the two branches, a full phase difference ranging from 0 ° to 360 ° with small phase deviation can be easily implemented. The parameters of the filtering branch can be derived by synthesis design based on the locations of transmission zeros (TZs). In addition, two isolation resistors are introduced to realize wideband isolation and a set of closed-form design equations is derived first. For verification, two prototypes with different PDRs and phase shifts are designed and fabricated. In particular, a multilayer strip-line structure is adopted to provide enhanced anti-electromagnetic (EM) interference capability and flexible EM coupling. Good agreement between simulated and measured results evidently reveals that the proposed design has attractive advantages of wide bandwidth, constant PDR, full phase difference range, and high port-to-port isolation.