Abstract Planomonads are widespread gliding zooflagellates from marine and freshwater sediments with seven species. We cultured 13 new strains; morphology and 18S and ITS2 rDNA sequences show that 11 represent eight new species described here. The 15 species form four robust clades, corresponding to revised Planomonas and Ancyromonas and new genera Fabomonas (marine) and Nutomonas (freshwater). Fabomonas tropica differs in shape and is genetically very distant from previously known planomonads, yet ultrastructurally similar. Anterior cilium morphology maps simply onto the rDNA tree forming the basis for two revised families: Ancyromonadidae (Ancyromonas, Nutomonas) have a uniformly thin, entirely acronematic anterior cilium; Planomonadidae (Fabomonas, Planomonas micra, and new species Planomonas elongata, bulbosa, and brevis) have a more conspicuous emergent basal region of the anterior cilium of normal thickness. ITS2 secondary structure is clade-specific, differing most sharply in the main Nutomonas subclade from all marine species, being exceptionally short compared with earlier-diverging marine clades. Nutomonas longa is very distant but Nutomonas howeae subsp. lacustris differs from Nutomonas (Planomonas) howeae and limna (new combinations) mainly by ITS2 compensatory and/or hemi-compensatory mutations. Ancyromonas indica, atlantica, and kenti are genetically more distinct from Ancyromonas sigmoides (=Planomonas mylnikovi). The first soil planomonad (new Nutomonas limna subspecies) was isolated.