Fish processing industries generate large quantities of waste materials such as scales, bones, skin, and viscera, which often create serious environmental pollution problems when discarded without proper management. Among these by-products, fish scales are considered a valuable natural source of hydroxyapatite, a calcium phosphate biomaterial widely used in biomedical and industrial applications. Hydroxyapatite possesses excellent biocompatibility, bioactivity, and structural similarity to human bone and teeth, making it highly suitable for tissue engineering and regenerative medicine. Recent studies have focused on recovering hydroxyapatite from fish scales using different extraction techniques including acid?alkali treatment, calcination, deep eutectic solvent extraction, and ionic liquid methods. Fish scalederived hydroxyapatite has demonstrated promising applications in bone tissue engineering, dental materials, wastewater treatment, drug delivery systems, and environmental remediation. In addition, the utilization of fish scale waste supports sustainable waste management and circular bioeconomy concepts by converting low-value biological waste into high-value industrial products. This article highlights the recovery methods, characterization, industrial applications, environmental significance, and prospects of hydroxyapatite obtained from fish scales.