This chapter reviews the applications of intumescence in the field of fire protection (resistance to fire) and fire retardancy (reaction to fire) of material. It starts describing the basics of intumescence and gives the main intumescent products available on the market associated with their typical application’s fields. It covers the reaction to fire of intumescent polymers and textiles including the latest developments of flame retardants as well as synergists. Resistance to fire is also considered using intumescent coating at the large and reduced scale. Mechanisms of action are always discussed considering the chemical, physical and thermal aspects.