Most people think of libertarianism as a right-wing political morality, but there are people (including some prominent philosophers) who defend a left-wing version of it. See here for an essay in which the author, Mathias Risse, questions the coherence of left-libertarianism. If you want a book-length defense of left-libertarianism, see here. Tom Palmer reviews the book here. Ian Carter reviews it here. David Gordon reviews it here. Gopal Sreenivasan reviews it here.