The question what antisemitism is and what are the appropriate means to fight it are definitely among the most contested questions of our time. Yet within these ongoing debates, revolving around history, society, and politics, the factor of religion is often pushed aside. Christosemitism sets out to fill this gap. An interdisciplinary research project sponsored by the European Research Council (ERC), Christosemitism studies the place of religion, and especially that of Christianity--the historical religion of Europe—in the fight against antisemitism in Western Europe between 1945 and 2020. We argue that the question what antisemitism is has been saturated with unacknowledged religious questions, such as what religion is, what is the right terlationship between religion and secularism, and what should be the place of the Christian religion in the rebuilding of war-wridden Europe. Christosemitism ivestigates these connections, exploring, on the one hand, why and how anti-antisemitism became a core component of the way in which Christianity is lived, practiced, navigated and polemicized in a secularizing continent, and, on the other hand, how the concept of antisemitism functions across secular-religious, intra-religious and inter-cultural tensions within Europe and between Europe and the world.