Glabrous perennial herbs; ± fleshy. Leaves opposite. Flowrs solitary in leaf axils. Calyx deeply 5-partite, lobes unequal in width, posterior broader. Corolla campanulate, subequally or ± unequally 5-lobed. Stamens 4, equal; anther loculi parallel, contiguous. Stigma subentire.Capsule 4-valved (loculicidal and septicidal); seeds very small, numerous.

About 100 species in tropics and subtropics. Represented in Pakistan by 1 species.

In the APG III classification (2009) Bacopa is included in the expanded family Plantaginaceae.