ENDefining the concepts of ‘vulnerability’ and ‘vulnerable groups’ is challenging, since vulnerability is a multi-dimensional concept used with both universal and particular meanings in a variety of disciplines, and can moreover be examined from different perspectives. In this chapter, we seek to define the concepts of ‘vulnerability’ and ‘vulnerable groups’ from sociological and legal perspectives in order to build a theoretical background for the subject analysed in this book. The approach taken in this chapter is based on the idea that to be human is to be vulnerable; nevertheless, although all humans are vulnerable, some groups are more vulnerable than others. The chapter begins with the sociological approach to vulnerability. It could be argued that contemporary societies consist of fragmented and often antagonistic communities with only a small number having access to adequate social welfare and services. The remaining individuals have little hope of realising their human potential. They are often called vulnerable or marginalised groups or groups at risk of social exclusion. In different spheres of life, vulnerable groups experience deep exclusion that negatively affects their quality of life, well-being and future life opportunities. Moreover, there exists a dominant discursive tradition that imposes a burden of guilt, shame and even greater vulnerability on socially afflicted and vulnerable groups. Rather than accepting this discursive tradition, sociologists have turned their attention to researching social exclusion, social suffering, and daily hardship, thereby turning vulnerable people’s experiences of injustice, harm and damage into crucial sociological issues.After a brief sociological analysis of vulnerable groups, the chapter continues by presenting the international legal framework. The authors identify and discuss the main universal and regional human rights instruments that provide for the protection of vulnerable groups and their individual members and note the relevant practice of the UN treaty monitoring bodies and UN Committees. In this way, the chapter sketches the framework of international legal regulation linking the international, regional and national levels. [From the publication]