<p>Hafnium oxide (HfO₂)-based ferroelectrics have garnered significant attention due to their compatibility with complementary metal–oxide–semiconductor (CMOS) processes, scalability down to sub-10&#xa0;nm thicknesses, and environmental stability. Unlike conventional perovskite ferroelectrics, HfO₂ exhibits robust ferroelectricity when doped or alloyed, particularly by stabilizing the non-centrosymmetric orthorhombic (<i>Pca2</i>_<i>1</i>) phase. Strategic incorporation of isovalent dopants such as Zr⁴⁺ and aliovalent dopants including La³⁺, Y³⁺, and Si⁴⁺ has been shown to enhance remanent polarization, suppress the monoclinic phase, and modulate oxygen vacancy dynamics. These doping strategies, combined with optimized deposition and annealing conditions, significantly improve key electrical properties such as leakage current, coercive field, endurance, and wake-up behavior. This review summarizes the mechanisms by which alloying and doping influence phase formation, structural distortion, and ferroelectric switching in HfO₂-based systems. Particular emphasis is placed on the role of dopants in domain wall mobility and defect dipole formation. The resulting performance improvements have enabled a wide range of applications, from ferroelectric random-access memory and ferroelectric field-effect transistor to piezoelectric sensors and neuromorphic computing elements. Remaining challenges, such as dopant uniformity, thermal stability during backend-of-line processing, and low-voltage operation, are also discussed. This work aims to provide a comprehensive understanding and guidance for the continued development of high-performance, CMOS-compatible ferroelectric materials.</p>