<p>Phytases have long been utilized in animal feeds to enhance phosphorus utilization and reduce the environmental impact of phosphorus-rich effluents. In aquaculture, the application of phytase has gained momentum over the past two decades due to growing concerns over phosphorus pollution in aquatic ecosystems. Exogenous phytase effectively hydrolyzes phytate, enhancing nutrient digestibility and reducing the need for inorganic phosphorus supplementation while minimizing phosphorus excretion in aquaculture. Given the non-renewable nature of global phosphate reserves, phytate, when supplemented with phytase, offers a sustainable and cost-effective phosphorus source. Despite its benefits, the use of phytase in fish feed remains limited compared to its application in poultry and swine, mainly due to its sensitivity to pH and temperature. However, recent studies have shown that phytase supplementation improves nutrient utilization, enhances digestibility and growth performance, and reduces phosphorus excretion—contributing to both fish health and environmental sustainability. This review outlines the types of phytase, their mechanisms of action, nutritional benefits in aquaculture species, and their role as growth promoters. It also highlights current challenges and limitations in their practical use, such as enzyme stability, optimal delivery methods, and species-specific responses. Finally, future prospects are discussed, with emphasis on genetic engineering approaches to develop novel phytases with improved stability and efficacy for broader application in aquaculture.</p>