Self-healing materials are attracting attention as materials for realizing a sustainable society because of their ability to recover their structure and function after damage. In this chapter, an overview of the design of polymers for self-healing materials is presented. Reversible cross-linking can achieve self-healing by effectively regenerating cross-links between polymer chains, since the cross-links can be repeatedly cleaved and reconnected. Noncovalent interactions such as hydrogen bonding, metal coordination bonds, ionic interactions, van der Waals forces, π-π stacking, host-guest complex formations with molecular size- or shape-specific recognition, etc. are used as reversible cross-linkings. In addition, noncovalent and dynamic covalent bonds that combine two or more of these interactions have been used. Multiple reversible cross-links create a synergistic effect, simultaneously achieving high toughness and effective self-healing properties. Some are able to regain their original shape and mechanical properties after cycles of external stress loading and unloading.