Abstract: A parasitic patch-loaded millimeter-wave broadband circularly polarized (CP) magneto-electric dipole (MED) antenna is proposed. The core innovation resides in adopting a synergistic optimization strategy integrating rotational symmetry structure modulation and dual-row rectangular parasitic patch loading, which enables the synchronous broadening of both impedance bandwidth (IBW) and axial ratio bandwidth (ARBW) while retaining the antenna's low-profile and compact features. The antenna employs a low-profile feeding configuration consisting of two pairs of rotationally symmetric patch structures, with the parasitic patches facilitating the excitation of a rotating electric field to realize stable CP radiation. To enhance the antenna gain, a 2×2 ME dipole antenna array was designed and tested. The measured results demonstrate an IBW of 51.21% (26.08–44.03 GHz) and a 3dB ARBW of 31.4% (32.09–44.03 GHz), with a maximum gain of 14.1dBic. Compared with state-of-the-art designs, the proposed antenna exhibits exceptional comprehensive performance in terms of bandwidth, gain, and compactness, rendering it a promising candidate for 5G millimeter-wave communications and satellite communication systems.