A novel type of E-plane S-shaped resonator loaded waveguide bandpass filter structure with enhanced stopband performance has been proposed. The structure has been easily realized with a single metalo-dielectric insert within the standard rectangular waveguide. The proposed structure maintains low-cost and mass producible characteristics while achieving significant size reduction. This kind of filters can be found applications particularly in the mm-wave, submm-wave and terahertz range circuits, e.g. in low phase noise oscillators and highly selective filters, diplexers and multiplexers, frequency selective surfaces and antennas.