Penstemon tenuis is a species of flowering plant in the plantain family known by the common name sharpsepal beardtongue.

It is endemic to Texas, Louisiana, Mississippi, and Arkansas in the United States where it is found in open, damp areas in alluvial soil.

[3] Penstemon tenuis is a perennial herb with erect, slender stems that can grow upwards of 3 ft (0.91 m) tall.

The leaves have pointed tips and toothed or entire margins.

The flowers are 0.5 in (13 mm) wide and slightly longer, and are bilabiate.