Why do countries pursue ambitious treaties with no practical chances of success? I argue that such treaties are utopian, and follow utopian political dynamics. In particular, they represent an attempt to establish and legitimize a normative vision and to build a status community of likeminded states around it. Over time, these efforts produce social and normative pressure which can meaningfully reshape the international system. I test this argument on two treaties -- the Kellogg-Briand Pact and the Treaty on the Prohibition of Nuclear Weapons. While meaningful differences exist between these utopian treaties, both demonstrate the long-run processes of utopian innovation and change I propose.