This chapter introduces the presence of the category of vulnerability in the bioethical context. It highlights the contributions of the main authors in the field and presents some of the taxonomies of vulnerability that have been rehearsed in time. It tracks the historical development of the term vulnerability in bioethics and differentiates the European approach, the North American principlism and the Latin American paradigm of the concept in Bioethics. It finally addresses the critiques and challenges of the vulnerability category in the field of Bioethics.