The smart properties of polysaccharides have been used by mankind long before the term “smart” was ever applied to materials. Polysaccharides also promise to become increasingly important due to the recent trend toward sustainability and the emergence of applications in the medical and life sciences. One theme of this chapter is that polysaccharides can confer smartness through somewhat unique mechanisms. For instance: (i) many polysaccharides undergo reversible, stimuli-responsive self-assembly (i.e., gelation); (ii) polysaccharides undergo biospecific interactions with enzymes and lectins (carbohydrate-binding proteins); and (iii) polysaccharides can undergo interactions that enable hierarchical supramolecular assembly. A second theme of this chapter is that there is a poor fundamental understanding of the molecular level interactions that confer smartness to polysaccharides. We anticipate that new experimental and theoretical tools will emerge to provide the necessary understanding of the structure–property–function relations that will enable polysaccharide-smartness to be understood and controlled. This enhanced understanding will complement the intrinsic characteristics of polysaccharides as sustainable, environmentally friendly and biologically compatible materials. Thus, we envision polysaccharides will continue to be well-positioned for applications in foods, cosmetics and medicine.