The theme of this thesis is interpretations of Immanuel Kant’s Perpetual Peace in the liberal peace debate from the 1980s and into the 2000s. The main research question is how these interpretations have made use of Kant, and a sub question is how Kant’s theories can be interpreted with regard to his own historical context. The liberal peace debate is situated in the middle of several scientific traditions: international relations; peace and conflict research; and political theory. The use of theory and methodology differ between the traditions, since classical international relations’ contributions seem to discuss Kant more in depth on a theoretical basis, while there is another strain that chooses an approach that is based on quantitative methodology. The general finding is that Kant’s theory of right (political, international and cosmopolitan) is interpreted to build up under the contemporary liberal state and its peacefulness. More specifically, the political right, in the form of the republican state, is interpreted as similar to the democratic liberal state. The international right is interpreted as representative of the interdependence of contemporary liberal states, while the cosmopolitan right is interpreted as contemporary liberal economy. However, I also find that there are specific historical and contextual traits to the Perpetual Peace that ought to be taken into consideration. Among them are Kant’s specific situation between the tradition of natural rights and the tradition of state of reason, and his particular views on citizenship and sovereignty in the republican state.