The genus Leiogalathea Baba, 1969 currently contains only two benthic species both occurring on the continental shelves and slope: L. laevirostris (Balss, 1913), widely reported in the Indo-Pacific region, and L. agassizii (A. Milne Edwards, 1880), from both sides of the Central Atlantic. A certain degree of morphological variability linked to their geographic distributions was previously noticed, mostly in L. laevirostris. In the present study, we revise numerous specimens collected from the Atlantic, Indian and Pacific Oceans, analysing morphological and molecular characters (COI and 16S rRNA). We found 15 new species; all of them are distinguished from L. laevirostris and L. agassizii by subtle but constant morphological differences and show clear genetic separation. Furthermore, L. imperialis (Miyake & Baba, 1967), previously synonymized with L. laevirostris, was found to be a valid species. All species are described and illustrated. Species of the genus Leiogalathea are morphologically distinguishable on the basis of the spinulation of the carapace, the shape and the armature of the rostrum, the shape of the propodi of the walking legs, and the pattern of the setae covering on rostrum, carapace and chelae. Some species are barely discernible on the basis of these characters but are highly divergent genetically.