Algae, including both microalgae and macroalgae, are increasingly recognized as sustainable food sources that can help ensure global food security while lowering environmental impacts. Rich in proteins, lipids, vitamins, minerals, and bioactive compounds, algae hold significant potential for use in functional foods, nutraceuticals, and innovative ingredients. Their rapid growth, capacity to fix carbon, and minimal land and freshwater needs make them climate-smart alternatives to traditional crops and animal-based proteins. This chapter emphasizes the nutritional value of algae, especially bioactive compounds like phycocyanin, astaxanthin, and polyunsaturated fatty acids, which are associated with antioxidant, anti-inflammatory, and cardioprotective benefits. Current obstacles include high production costs, limited large-scale processing technology, and regulatory barriers that slow market adoption. Nonetheless, advancements in cultivation techniques, extraction methods, and biorefinery approaches are enhancing economic viability. This chapter also examines how algae contribute to sustainable food systems through phycoremediation, nutrient recycling, and integration with aquaculture and agriculture. Future outlooks highlight the importance of interdisciplinary research, consumer acceptance, and supportive policies to expand algae-based foods worldwide. Thus, algae represent a promising pathway toward developing climate-resilient, health-promoting, and resource-efficient food systems.