In the post-Cold War era, the discussion on human rights and its promotion at the international level has proliferated, and this has coincided with a growing tendency to see a linkage between violations of human rights and international security. Drastic changes in international relations since the end of the Cold War have increased the probability of intervention with or without UN Security Council authorisation. Thus, the debate about humanitarian intervention has been reheated, generating a considerable literature, besides the increasing state practice. This article is an attempt to comprehend and illuminate this controversial issue. In doing so, after touching upon the definition of the concept, this article will discuss the evolution of the idea and practice of humanitarian intervention. By this means, the way in which the concept of humanitarian intervention has changed in accordance with the changing international milieu will be underlined. This article thus puts forward the view that humanitarian intervention is a reflection of a wider debate in international relations, namely cosmopolitanism vs. realism and, as such, it represents a shift from a statist paradigm to growing cosmopolitanism.