Magnesium-based metal matrix composites (MMCs) have emerged as promising lightweight materials with high strength, wear resistance, and thermal stability for applications in aerospace, automotive, and biomedical sectors. This chapter reviews key fabrication methods, including liquid-state processing, solid-state processing, and in situ synthesis, each offering distinct advantages and limitations. Liquid-state techniques—such as melt infiltration, ultrasonic infiltration, squeeze casting, stir casting, and disintegrated melt deposition—enable large-scale production and uniform reinforcement distribution, though challenges of wettability and agglomeration persist. Solid-state routes, including powder metallurgy, additive manufacturing, microwave sintering, and severe plastic deformation, allow fine microstructural control while minimizing defects. In situ synthesis methods further enhance bonding by generating reinforcements directly within the magnesium matrix. The chapter also discusses novel reinforcements such as high-entropy alloys, metallic glasses, and syntactic foams, which significantly improve strength-to-weight ratio, corrosion resistance, and energy absorption. Collectively, these fabrication approaches advance the development of high-performance magnesium composites for next-generation engineering applications.