The sparassid genus Macrinus Simon 1887 is revised, the type species, M. succineus Simon 1887, is redescribed and Olios pollexensis Schenkel 1953 is transferred to the genus. Females are described and illustrated for the first time. Macrinus milleri Caporiacco 1955 is placed as incertae sedis and a new species, Macrinus jaegeri, is described from the states of Pará and Mato Grosso, Brazil.