Ascidia mentula is a species of solitary tunicate. It is found in the north east Atlantic Ocean, the Mediterranean Sea and Black Sea. It occurs round the coasts of Britain but is seldom seen on the east coast of England or Scotland. Ascidia mentula has a tough leathery envelope or tunic composed partly of cellulose. The translucent tunic encloses a fluid-filled body with irregular bulges and two unmistakable siphons.