The concept of vulnerability and, more specifically, its use in bioethics and in the philosophy of medicine, is at the heart of hotly contested debates. Deemed overly paternalistic, stigmatizing, and conceptually-flawed, and yet still deeply relevant and useful, it has been reworked and complexified in order to offer a more accurate understanding of what it means to be—medically—vulnerable. It is the aim of this chapter to propose an overview of the diverse manners in which vulnerability was conceptualized. Firstly, it will provide a few conceptual clarifications regarding the link between vulnerability and other closely related concepts such as risk and susceptibility. It will then analyze shifting views regarding who is mostly concerned by the concept: is it to be ascribed to specific groups whose ability to make autonomous decisions and to protect their own interests is questioned, to humanity as whole by virtue of being interdependent, needful corporeal beings, or to individuals whose bodies and circumstances vary greatly? Secondly, it will present different views on what exactly vulnerability is: a limitation to one’s autonomy or the complex intertwinement of contextual and individual features? Lastly, this chapter will propose a brief outlook on how the concept of vulnerability can be integrated into a series of questions central to the philosophy of medicine and present two conceptualizations of vulnerabilities that might prove pertinent in this context: Rogers, Mackenzie, and Dodd’s taxonomy of inherent, situational, and pathogenic vulnerabilities and Luna’s layers of vulnerability.