This dissertation focuses on Catholic sisters in modern Germany, with a particular emphasis on Nazi Germany. In the 1930s, nearly one hundred thousand nuns lived in Germany; this figure compares to about 22,000 priests. I present a representative case study of the Poor School Sisters of Notre Dame. With about 4,000 members, the institute of the Poor School Sisters of Notre Dame was one of the largest teaching congregations in Germany in the 1930s. My work destabilizes common historical narratives that associate women's progress in the modern era only with secularization. Catholic religious vocations in fact offered countless women an alternative to marriage, a higher education, and the chance to enter a profession at a time when opportunities for women contracted in the secular realm. But longstanding saccharine and mocking portrayals of nuns in popular culture, such as in films like The Sound of Music and Sister Act, have contributed to the dismissal of nuns in the modern era as serious historical actors. Clichés of nuns are in fact linked to the women's contested status in patriarchal Western society that expressed common anxieties about women foregoing marriage and childbearing in favor of a life of public service in all-female communities. These age-old tensions between the social and sexual demands placed on women and women's continued insistence on religious vocations reached a zenith in Nazi Germany. The history of Catholic sisters illuminates the contested position of the Catholic Church in Hitler's Germany between privilege and oppression. The women worked to integrate into the Nazi state and through their labor in schools, the Poor School Sisters both legitimized and subverted the regime. Although the sisters tried to assimilate, they remained on the fringes of Hitler's 'people's community.' When the Nazis attempted to remove nuns from the public sphere, the women learned that they could not rely on the clergy to come to their aid and they formulated an independent response to National Socialism. The Poor School Sisters relied in part on popular support to preserve their privileged position in society, and my work therefore adds new insights to key debates on Nazi Germany as a dictatorship of consent. The history of nuns exposes the extent to which Hitler depended on ordinary Germans to participate in the persecution of outsiders. For instance, in 1935 the Nazis orchestrated a series of sensational criminal legal proceedings against nuns in order to persuade Germans to turn against the women and the church. Although the Nazis used many of the same measures against nuns as against Jews, most people refused to shun the women because in their case, crucial pre-conditions for persecution, in particular latent prejudices and opportunities for self-advancement, were absent. I reject ubiquitous depictions of nuns in the scholarship as victims of Nazism. I argue instead that despite Catholic sisters' dismissal from schools, their sphere of influence in Germany actually increased in the latter 1930s, as they took up positions as social workers and pastoral assistants across the country. Nuns also occupied key positions during World War II, and their lives frequently intersected with Nazi criminal and ideological measures. My research adds fresh perspectives to central discussions on women and the church in war and the Holocaust. Catholic sisters' participation in the war effort was extensive. I challenge common portrayals of women as mere helpmates to men, which contributed to postwar narratives of women as apolitical and powerless victims of war and Nazism. Women did not merely perform subservient work for absent men. The history of Catholic sisters shows that the women contributed their sophisticated organizational networks and real estate and their and skilled 'feminine' labor to the German war effort. My research also highlights young Catholic women's increased active political involvement in the National Socialist cause in the latter 1930s and 1940s. In particular during war, the Nazis successfully persuaded many young candidates for sisterhood to forego religious life in favor of working for the Nazi movement. The drastic decline in religious vocations in the 1940s was in part due to the unprecedented expansion of young, single women's public roles in Hitler's Germany and occupied Europe. The Poor School Sisters of Notre Dame emerged from the Third Reich with their communities intact, but they also lost a generation of sisters to National Socialism, and thus diminished, they struggled to meet the great demands placed on them in postwar West Germany.