| Lobelia fenestralis Cav., 1801 |
| Lobelia fissa Willd. ex Schult., 1819 |
| Lobelia flexicaulis Rzed. & Calderón, 2001 |
| Lobelia flexuosa (C. Presl) A. DC., 1839 |
| Lobelia flexuosa subsp. intermedia (Hemsl.) Lammers, 2006 |
| Lobelia fulgens Humb. & Bonpl. ex Willd., 1809 |
| Lobelia ghiesbreghtii Decne., 1848 |
| Lobelia gladiaria McVaugh, 1949 |
| Lobelia glaucescens E. Wimm., 1953 |
| Lobelia goldmanii (Fernald) T.J. Ayers, 1990 |
| Lobelia gracilens A. Gray, 1886 |
| Lobelia graminea Lam., 1792 |
| Lobelia grandidentata C. Presl, 1836 |
| Lobelia gruina Cav., 1800 |
| Lobelia gruina var. conferta Fernald, 1901 |
| Lobelia guerrerensis Eakes & Lammers, 1999 |
| Lobelia guzmanii Rzed., 2016 |
| Lobelia gypsophila T.J. Ayers, 1988 |
| Lobelia haenkeana (C. Presl) A. DC., 1839 |
| Lobelia hartwegii A. DC., 1839 |