Abstract-New zeroth-order resonators (ZORs) are utilized as parasitic elements to enhance a microstrip antenna's bandwidth. By utilizing mushroom T/L shaped resonators, extra resonances are generated. Then, by merging the resonances of the microstrip antenna and the T/L shaped resonators, a wideband antenna is obtained to cover the 5.15-5.35 GHz wireless local area network (WLAN) band. As the ZORs are embedded in the patch of the microstrip antenna, the usages of the parasitic elements do not increase the antenna size. Moreover, as one ZOR resonance is lower than the microstrip patch resonance, a compact antenna is realized. The patch size is decreased from 0.27λ c ×0.42λ c ×0.027λ c of the reference microstrip antenna (RMA) to 0.25λ c × 0.40λ c × 0.026λ c of the proposed ZOR based microstrip antenna, where λ c is the wavelength of their corresponding lower cutoff frequencies. The proposed antenna was fabricated and measured. The simulated and measured −10 dB impedance bands of the proposed antenna are 5.06-5.40 GHz and 5.07-5.42 GHz, respectively. And, its bandwidth increases 70% compared to the RMA. The simulated and measured patterns are stable in the whole operating band. The gains of 4.73 dBi and 4.24 dBi are measured at the ZOR modes, and 7.88 dBi is measured at the microstrip patch mode.