Osmadenia is a genus of flowering plants in the family Asteraceae.

It contains the single species Osmadenia tenella, which is known by the common name false rosinweed.

Osmadenia tenella is a hairy, glandular, aromatic annual herb producing an erect stem approaching 40 centimeters (16 inches) in maximum height with threadlike branches.

The linear leaves are alternately arranged, the largest low on the plant measuring up to 5 centimeters.

[2] The fruit is an achene; those arising from disc florets have pappi.