Onomarchus[1] is a genus of bush crickets or katydids found mainly distributed in the tropical forests of Asia.

Like many other members of the subfamily Pseudophyllinae, their wings appear very leaf-like.

A study of O. uninotatus found it to produce sounds at an unusually low frequency of about 3.5 kHz.

The tympanal membrane cuts out high frequencies unlike the sound filters found in other Tettigoniids.

[2] The species in the genus include