Abstract: To meet the miniaturization and low-power requirements of antennas for portable low-frequency undersea communication systems, a super-low-frequency (SLF) magnetoelectric mechanical antenna based on an integrated bias FeGa/Steel/PZT heterostructure is proposed in this work. Theoretical analysis demonstrates that, compared to conventional structures, the additional steel layer provides additional design degree of freedom, which can be utilized to enhance converse magnetoelectric effects. Furthermore, the bias structure is optimized and integrated into the antenna, which provides a better bias magnetic field for the FeGa layer. The proposed bias structure can further enhance converse magnetoelectric effects, realizing enhanced radiation performance and antenna miniaturization. Based on the proposed integrated bias FeGa/Steel/PZT structure, a SLF magnetoelectric mechanical antenna was designed, fabricated, and measured. The antenna dimensions are 80 × 20 × 2.65 mm³. Measurement results show a resonant frequency of 292 Hz. Under a 10 V excitation voltage, it achieves a radiated magnetic flux density of 5.83 nT at a distance of 1 m, with an input power of only 5.83 mW. The measured results exhibit good agreement with simulation results. This antenna features miniaturization, a compact structure, and low power consumption, offering a novel antenna structure and a new design method for portable low-frequency underwater communication systems.