Fish processing generates large quantities of by-products, including heads, bones, skin, viscera, and scales, which pose environmental and economic challenges if discarded. These residues, rich in lipids and proteins, can be valorised for sustainable bioenergy production. Lipid-rich waste is converted into biodiesel, protein- and collagen-rich fractions into bioethanol, and mixed residues via anaerobic digestion produce methane-rich biogas. This integrated approach supports a circular economy, reduces carbon emissions, and provides additional income streams for the fisheries sector. Advances in microbial and pre-treatment technologies enhance energy yield and process efficiency, making fish waste a promising renewable energy resource.