The halogen bond may be considered as a special case of sigma-hole bonding, wherein an electron donor interacts with the electrophilic region of a halogen atom. Within this broader picture, sigma-hole bonding can encompass a range of non-covalent interactions which are named after the atom bearing the electrophilic region, also known as the sigma-hole. This Faraday Discussion unites experimentalists and theoreticians, who are pushing the applicability of this broad class of interactions far beyond only the halogens. The book develops a fundamental understanding of key aspects of non-covalent interactions in solid-state materials, solution chemistry, biochemistry and the gas phase.