A novel wideband circularly polarized microstrip patch antenna (MPA) with multimode resonance is proposed in this letter. The TM1/2,0 mode, the zeroth-order mode, and the TM1,0 mode are excited by inserting the shorting pins underneath the driven patch and the parasitic patch. Therefore, a wide impedance bandwidth is achieved under triple-mode resonance. By sequentially rotating the triple-mode elements, a circularly polarized MPA is developed with a four-feed network. Additionally, four metallic side walls are employed to obtain desirable radiation performances. For demonstration, a prototype of the proposed antenna is fabricated and measured. The measured-10 dB impedance bandwidth is 96% (1.53-4.39 GHz) and 3 dB axial ratio bandwidth is 86% (1.74-4.36 GHz). Meanwhile, a low profile with the height of 0.037λ0 (λ0 is the wavelength in free space at the lowest operating frequency) is obtained. Such a wideband, low-profile, and circularly polarized antenna is very promising for modern wireless communication applications.