Macroalgae are a promising source of nutritional ingredients including proteins, polysaccharides and minerals. The need to increase animal and feed production has increased interest in macroalgae as underutilised resources with promising applications as alternative animal feeds. This chapter summarizes the nutritional attributes of macroalgae in terms of macro and micronutrients as a source of protein and other compounds in pig nutrition. The benefits of macroalgae or macroalgal derived extracts in feed are discussed together with future trends and challenges in the development of effective feed formulations.