Hydrogels are special polymer systems with unique properties due to their high-water content. They hold a relatively large importance in several application fields, especially in the medicine and sanitary products. Moreover, their potential utility is intensively studied in several other fields. While most commercially available hydrogels are synthetic polymer-based, there is an increasing interest in the use of various renewable resources. Such materials have several advantageous properties, like biodegradability and good biocompatibility. Polysaccharides are the most important group of the renewable materials due to their abundance and low cost. In the present chapter, we give an account of the potential use of polysaccharide systems for the formation of hydrogels. After a short introduction to the chemical structure of polysaccharides, their dissolution, possible crosslinking methods, and the studies related to the most important representatives are discussed. The modification of gel properties by grafting, copolymerization, and blending is also a very common route. The non-polysaccharide component can range from other renewable resources like polypeptides to synthetic polymers to inorganic additives. Finally, we give a summary of the potential applications of the polysaccharide-based hydrogels.