The concept of a “United States of Europe” has been a recurring idea in European political discourse, suggesting a federalist approach to European integration. This article explores the historical roots, interwar debates, and feasibility of such a political entity. It delves into the challenges posed by differing political ideologies within Europe, especially during the interwar period. The idea of a United States of Europe was promoted by human rights leagues and Freemasonry. The article brings this to the fore. Through examining various perspectives, the article aims to contribute to the ongoing dialogue surrounding the prospects and implications of a United States of Europe.