Three new continental and one new insular species of the gekkonid genus Cnemaspis Strauch 1887 are described from southern Vietnam based on their unique combinations of morphological and color pattern characteristics. The presence of these species in small, isolated mountains in the Mekong Delta flood plain and on one of the many small islands in Rach Gia Bay indicates that additional new species are likely to occur in these and similar underexplored regions in southern Vietnam. The discovery of new species of Cnemaspis in southern Vietnam narrows a 630 km distribution gap across the Indochinese Peninsula to a hiatus of 315 km. This report demonstrates that continued systematic field research is necessary in southern Vietnam before its herpetofaunal biodiversity will be fully realized and effective conservation measures can be put into place to protect it.