In this presentation I summarise the multitude of distinct ways the term autonomy is used in bioethics, in moral, social and political philosophy, and in common usage. My aim is to urge bioethicists to be vigilant with respect to which sense of the term is being employed in a particular argument. I show that distinct senses of autonomy are sometimes conflated in the bioethics literature. Further, the justification that a person’s autonomy is due respect depends upon the sense in which the term ‘autonomy’ is being employed. Different justifications can then fundamentally affect the broader arguments in which the principle of respect for autonomy is being cited. I shall illustrate my points with examples from end-of-life ethics, concentrating on the distinction between autonomy as negative liberty and autonomy as a form of positive liberty.