In this paper, a new structure is introduced to design resonators with very short length and without any discontinuity. The introduced structure, called Nonuniform Impedance Resonator (NIR), is an openor short-circuited Nonuniform Transmission Line (NTL). To synthesize NIRs, strip width or the characteristic impedance function of the microstrip NIRs is expanded in a truncated Fourier series, first. Then, the optimum values of the coefficients of the series are obtained through an optimization approach. The usefulness of the proposed method is verified using some examples.