Information concerning mineral nutrition of fish and marine crustaceans is rather limited compared to that available for terrestrial animals; however, significant advances have been made in recent years. This article summarizes pertinent information about mineral nutrition of fish and marine crustaceans, including classification and general functions of the minerals; dietary essentiality and/or quantitative requirements; bioavailability and dietary interactions; and general recommendations for dietary supplementation. Dietary requirements for approximately ten minerals (calcium, copper, iodine, iron, magnesium, manganese, phosphorus, potassium, selenium, and zinc) have been identified for fish, and seven minerals (calcium, copper, phosphorus, potassium, magnesium, selenium, and zinc) have been recommended for inclusion in penaeid shrimp and lobster feeds. Based on current literature, it is clear that when evaluating the dietary essentiality of a mineral, not only growth must be evaluated, but also tissue stores, biochemical indicators (e.g., enzyme reaction rates), and effects on the general development of the animal should be assessed. Due to limited studies concerning dietary mineral requirements of marine fish and crustaceans, methodologies and requirement estimates for other species are recommended as guides for research with marine fish and crustaceans.