This review discusses the extraction of collagen from fish by-products using various methods and their applications in biomedical, food, and cosmetic sectors. Fish by-products, such as heads, skins, viscera, and scales, constitute a significant portion of fish waste, with only 25% being utilized, while the remaining 75% is considered waste. Collagen extracted from these by-products has potential applications in biomedical, food, and cosmetic industries due to its biocompatibility, biodegradability, and functional properties. The review highlights several extraction techniques, including acid-soluble collagen (ASC), enzyme-soluble collagen (ESC), ultrasound extraction, deep eutectic solvent (DES) extraction, and supercritical fluid extraction (SFE). Each method involves different parameters such as time, temperature, solid-to-liquid ratio, and solvent/pepsin concentration, which affect the yield and quality of collagen. The review also discusses the applications of fish collagen in biomedical contexts, such as wound healing, tissue engineering, drug delivery, and cell culture. In the food sector, collagen is used as a food additive and in the production of collagen supplements and drinks. In cosmetics, collagen is used to improve skin texture, moisture, and appearance. The review concludes that fish-derived collagen has significant potential for various applications, and further research is needed to optimize extraction methods and explore new applications.This review discusses the extraction of collagen from fish by-products using various methods and their applications in biomedical, food, and cosmetic sectors. Fish by-products, such as heads, skins, viscera, and scales, constitute a significant portion of fish waste, with only 25% being utilized, while the remaining 75% is considered waste. Collagen extracted from these by-products has potential applications in biomedical, food, and cosmetic industries due to its biocompatibility, biodegradability, and functional properties. The review highlights several extraction techniques, including acid-soluble collagen (ASC), enzyme-soluble collagen (ESC), ultrasound extraction, deep eutectic solvent (DES) extraction, and supercritical fluid extraction (SFE). Each method involves different parameters such as time, temperature, solid-to-liquid ratio, and solvent/pepsin concentration, which affect the yield and quality of collagen. The review also discusses the applications of fish collagen in biomedical contexts, such as wound healing, tissue engineering, drug delivery, and cell culture. In the food sector, collagen is used as a food additive and in the production of collagen supplements and drinks. In cosmetics, collagen is used to improve skin texture, moisture, and appearance. The review concludes that fish-derived collagen has significant potential for various applications, and further research is needed to optimize extraction methods and explore new applications.