A quintuple-mode wideband bandpass filter (BPF) on a single circular waveguide cavity with perturbation-oriented cylinders is proposed. These five resonant modes are the fundamental TM mode, a pair of TM degenerate modes, and a pair of TE degenerate modes. Three metallic cylinders are installed on the bottom of an intra-cavity to excite TM modes, and two coaxial feed probes are used to further separate the paired TE modes. A wide passband under the resonance of these five modes is achieved with 36% fractional bandwidth. To prove the validity, the proposed filter is fabricated using silver-plated aluminum metal cavity. The measured results are in good agreement with the simulated results.