Mesochaete undulata is a moss found in Australia and Lord Howe Island.

Usually seen in moist sites on rocks or soil beside streams.

Plants may be large, up to 5 cm long.

The stems are usually not branched, red at the base and yellowish green above.

This plant first appeared in scientific literature in 1870, published in the Botanical Journal of the Linnean Society by the Swedish bryologist, Sextus Otto Lindberg.