Botrylloides violaceus is a colonial tunicate of the genus Botrylloides. Its native range is the in Northwest Pacific from Southern China to Japan and Siberia. Colonies attach and grow on solid surfaces and substrates, and consist of individuals arranged in twisting rows. Outside its native range, it is considered an invasive species and are becoming more common in coastal waters of North America and other waters around the world, likely being spread by shipping industries.