This paper proposes a compact bandpass filter using a folded ring resonator, which occupies an area, one-quarter the size of a conventional ring resonator. For the filter design, circuit modeling is used to derive the coupling coefficients between the even-and odd-mode resonances of the proposed resonator with the perturbation stub. The validity of the proposed filter is demonstrated by designing and fabricating a two-pole bandpass filter with a 100 MHz bandwidth at the central frequency of 2.45 GHz.