Boltenia villosa is a species of tunicate, a marine invertebrate of the family Pyuridae. Common names include the spiny-headed tunicate, the hairy sea squirt, the stalked hairy sea squirt and the bristly tunicate. This species was first described in 1864 by the American marine biologist William Stimpson who gave it the name Cynthia villosa. It was later transferred to the genus Boltenia. The type locality is Puget Sound, Washington state, United States.