This review presents a comprehensive and precise summary of the hydrothermal synthesis and morphology control of zinc oxide (ZnO) nanomaterials, the advantages of hydrothermal synthesis, and the wide range of applications. ZnO nanomaterials have garnered significant attention in recent years for their diverse applications across various industries owing to their unique properties and versatility, with practical applications in healthcare, cosmetics, textiles, automotive, and other sectors. Specifically, the ability of ZnO-based nanomaterials to promote the production of reactive oxygen species, release of Zn²⁺ ions, and induce cell apoptosis makes them well-suited for bio-medicinal applications such as cancer treatment and microorganism control. Hydrothermal technique offers precise control over the synthesis of ZnO, metal/non-metal-doped ZnO, and related composites, enabling the tailoring of properties for specific applications. The significant feature of the hydrothermal technique is the use of water as a solvent, which is cheap, available, and environmentally benign. In the last section, we discussed the potential future direction of ZnO-based research.