This volume is a monograph of the 47 species of the Dulcamaroid clade of the large and diverse genus Solanum. Species in the group occur in North, Central and South America, and in Europe and Asia. The group is most species-rich in Peru and Brazil, and three of the component species, Solanum laxum of Brazil, Solanum seaforthianum of the Caribbean and and Solanum crispum of Chile are cultivated in many parts of the world. All species are illustrated and a distribution map of each is provided. All names are typified and nomenclatural and bibliographic details for all typifications presented. One new species from Ecuador is described. The monograph is the first complete taxonomic treatment of these species since the worldwide monograph of Solanum done by the French botanist Michel-Felix Dunal in 1852.