Abstract: This paper proposes a low-profile wideband magnetic-coupling patch antenna designed to alleviate the considerable pressure caused by the antennas on the 5G mobile terminal metal frame. This small planar antenna can be mounted on the back cover of terminal devices with large available space, thus reducing the stress on the frame. The magnetic-coupling parasitic loading method is employed to enhance bandwidth. Based on the first two modes of the half-mode patch antenna, this paper derives a parasitic half-mode patch with a back-to-back topology. Each fundamental mode can be extended into two modes characterized by even and odd symmetry in their current field distribution. With no radiating nulls, consequently, four resonances are generated within the passband. To achieve miniaturization, two slots are etched around the wider edge, while a ring slot surrounding the feeding probe is utilized for impedance matching. Finally this paper obtains a low-profile wideband patch antenna. The profile of the proposed antenna measures 1.5 mm (0.015 λ_L), and its dimensions are 35.0 mm×36.3 mm(0.36λ_L×0.37λ_L). The antenna has been fabricated and measured, and the results indicated that the -6 dB impedance bandwidth of 3.05 GHz~4.27 GHz (33.3%), effectively covering the desired 5G band N77 (3.3 GHz~4.2 GHz) with the minimum total in-band efficiency is -1.9 dB (64.6%). In this paper, a new parameter, bandwidth volume ratio (BVR), is defined to measure the volume utilization. The proposed antenna has the higher space utilization compared with the existing wideband patch antennas.