Rossioglossum williamsianum is accepted species in  the family Orchidaceae  subfamily: Epidendroideae, tribe: Cymbidieae, subtribe: Oncidiinae,  
Genus Rossioglossum 
Infraspecific taxa recognized within Rossioglossum williamsianum: infraspecific taxa
This species is found in Mexico (Oaxaca, Chiapas) to Honduras.