The sustainable production of marine ingredients is a critical focus for manufacturers, governments, authorities, and environmentally conscious consumers. This Special Issue showcases cutting-edge advancements in biotechnologies for the sustainable development of ecologically important marine resources. Of the 15 papers received, 12 highlight the production and application of n-3 long-chain (LC, >=C20) polyunsaturated fatty acids (n-3 LC-PUFAs) in aquaculture feeds and nutraceuticals. Key topics include the following: Single-cell production of n-3 LC-PUFAs; Recent breakthroughs in n-3 LC-PUFA oilseed production and regulatory insights; Lipidomic analysis and sustainability of the New Zealand green shell mussel (GSM);Insights into the utilization of myctophid fish for n-3 LC-PUFAs;Omega-3-related studies in northern Australian beef cattle and squid viscera oil production; Additional contributions explore sustainable practices in krill aquaculture and fishery management, marine-safe biosurfactants, and innovative techniques like compound-specific stable isotope analysis for determining the provenance of marine-derived products, such as squalene. This Special Issue collectively underscores significant advancements in omega-3 research and broader marine biotechnologies, providing valuable insights for sustainable innovation.