Marine plants such as algae, seagrasses, and mangroves are important because they contain various polysaccharides with biological activities such as anti-inflammatory, antimicrobial, antioxidant, and anticancer, and properties such as multifunctionality, natural abundance, biodegradability, and minimal toxicity. The increase in industrial and dietary use of various plant-based polysaccharides such as alginate, carrageenan, fucoidan, ulvan, and agar, which are found in high amounts in the dry biomass of seaweeds, has a global economic impact. Plant-based marine polysaccharides (PMPs) are intensively used as food additives due to their stabilizing, gelling, thickening, fat replacement, and prebiotic properties in the industry. In addition, PMPs have become popular in the packaging industry as an alternative to plastic packaging materials due to environmental and health concerns, as environmentally friendly, renewable, biodegradable, and nontoxic materials. The high demand for functional foods containing bioactive component-loaded carrier systems has popularized the use of PMPs in encapsulation technology due to their high binding, carrier, and stabilizing properties. Moreover, due to the recent high demand for foods with personalized nutritional values, the use of PMPs as building materials in 3D printing applications has gained importance. In this section, food applications of PMPs are explained in detail.