Liogenys Guérin-Méneville, 1831 is the major genus of Neotropical Diplotaxini, with 78 species distributed from Panama to southern Argentina and Chile, except for Ecuador. Due to the large numbers of both described and undescribed species, as well as its agricultural importance, mainly of those in Brazil, Liogenys was redefined and redescribed. Nine new species are described: L. cavifrons Cherman, sp. n., L. femella Cherman, sp. n., L. piauiensis Cherman, sp. n., L. rotundicollis Cherman, sp. n., L. pseudosanctaecrucis Cherman, sp. n., L. grossii Cherman, sp. n., L. pseudospiniventris Cherman, sp. n., L. sulcoventris Cherman, sp. n., and L. freyi Cherman, sp. n. All the new species are Brazilian, except for the last one, which is Argentinian. Twenty-three Brazilian species are redescribed and illustrated. Five new synonyms are proposed, and 19 lectotypes are designated. New geographical distribution records for 19 species are presented, as well as a key to New World Diplotaxini and Brazilian species of Liogenys.