We here describe Liodessus lacunaviridis sp. n. (Coleoptera: Dytiscidae, Bidessini), collected from small mossy puddles at the edge of the Laguna Verde, Boyaca, Colombia. Within Liodessus Guignot, 1939 the new species is well characted by its darker coloration, more elongate oval habitus, and the shape of the median lobe in ventral view, which is more evenly narrowing than in the other Andean species known so far. In addition to external morphology, we used mitochondrial cox1 sequence data to support the generic assignment and delineate the new species. Altogether 32 species of the genus are now known from the Americas, 12 of them from the Andean region.