Orthomorpha is a genus of millipedes in the family Paradoxosomatidae containing approximately 50 species distributed in Southeast Asia.
Species of Orthomorpha possess 20 body segments and range from 15–50 mm long as adults. They range from 1.1–3.1 mm in body width, with prominent paranota (lateral keels) extending the width to 1.5–6.7 mm. Base coloration varies from brown to black, with brightly colored paranota and markings in various shades of yellow, orange, and brown, which becomes fainter in alcohol-preserved specimens. Some species have prominent bumps or "tubercles" on their dorsal metatergal segments.
Orthomorpha species range from Myanmar in the west, through the entire Indochinese Peninsula, to Lombok, Indonesia. The species O. coarctata, (also known as Asiomorpha coarctata) has been widely introduced by humans in tropics around the world.
