Lobelia is a genus of flowering plants in the family Campanulaceae comprising 415 species, with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions. They are known generally as lobelias.

The family Campanulaceae, of the order Asterales, contains nearly 2400 species in 84 genera of herbaceous plants, shrubs, and rarely small trees, often with milky sap. Among them are several familiar garden plants belonging to the genera Campanula (bellflower), Lobelia, and Platycodon (balloonflower). Campanula rapunculus and Codonopsis lanceolata are eaten as vegetables. Lobelia inflata, L. siphilitica and L. tupa and others have been used as medicinal plants. Campanula rapunculoides may be a troublesome weed, particularly in gardens, while Legousia spp. may occur in arable fields.