Lobelia hongiana, a new species of Campanulaceae from Guangxi, South China, is described and illustrated here. This new species is most similar to L. chinensis and L. loochooensis, but differs by its ellipticobovate or oblanceolate leaf, 2.5–3 mm long greenish-carmine hypanthium, 5 or 6 calyx lobes, purplishwhite corolla, with yellowish-green blotches at the base of lower lobes, glabrous filaments, 7–8 mm long broadly obconic capsule. Molecular phylogenetic analysis has been conducted based on ITS and two chloroplast sequences (atpB and rbcL) and 14 taxa in Lobelia are included. L. hongiana is well supported as a new species by the evidence from both morphology and molecular phylogeny.