Lobelia lithophila Senterre & Castillo-Campos (Campanulaceae, Lobelioideae) is described as a new species from the lowland tropical evergreen rainforest of the region of Uxpanapa, in southern Veracruz, Mexico. This species is only known from the type locality and probably represents a microendemic. The species described is most closely related to L. orientalis Rzedowski & Calderón, another local endemic from Querétaro, Mexico. Both taxa combine the herbaceous life form with leaves more or less in a rosette at ground level and a completely superior ovary, and are from specialized habitats. The new species is easily distinguished by its longer leaf blade and smaller petiole, and by its reduced leaf pubescence. Its habitat is also unusual, as it is restricted to limestone rocks in the understory of lowland tropical rainforest. Lobelia lithophila belongs to subsection Leiospermae E. Wimmer within the section Lobelia, subgenus Lobelia L.