Abstract: Against the backdrop of the global automotive industry's transition toward low-carbon and electrified development, lightweighting technology has become a key competitive factor. Magnesium alloys, owing to their low density, high specific strength, and resource endowment advantages, are deeply integrated with integrated die-casting technology, demonstrating significant application potential. This paper systematically reviews the current development status of integrated magnesium alloy die-castings in the automotive sector. First, it analyzes the dual drivers of lightweighting—namely, carbon peak and neutrality goals and range anxiety—and elaborates on the physical properties of magnesium alloys and their compatibility with die-casting processes. Second, it outlines the material systems of die-cast magnesium alloys, including mainstream base materials such as the AZ and AM series, as well as newly developed heat-resistant magnesium alloys enhanced via microalloying with elements like rare earths, Ag, and Sn. Third, it summarizes the application progress of magnesium alloys in typical components such as body structures and electric drive housings, with a focus on key process technologies including semi-solid forming and anti-corrosion treatments. Meanwhile, the current landscape of the magnesium alloy die-casting industry, including the strategies of OEMs and foundries, is also discussed. Finally, the paper addresses major challenges in the application of magnesium alloys, such as poor corrosion resistance, limited strength and plasticity, and inadequate joining technologies. It also highlights future trends, indicating that under the impetus of falling magnesium prices, process advancements, and the growing demand from new energy vehicles, magnesium alloy die-castings are evolving toward larger sizes and load-bearing structural applications. This review aims to provide a reference for further research and industrial application of magnesium alloys in automotive lightweighting.