The Reichskonkordat ("Concordat between the Holy See and the German Reich") is a treaty negotiated between the Vatican and the emergent Nazi Germany. It was signed on 20 July 1933 by Cardinal Secretary of State Eugenio Pacelli, who later became Pope Pius XII, on behalf of Pope Pius XI and Vice Chancellor Franz von Papen on behalf of President Paul von Hindenburg and the German government. It was ratified 10 September 1933 and it remains in force to this day. The treaty guarantees the rights of the Catholic Church in Germany. When bishops take office, Article 16 states they are required to take an oath of loyalty to the Governor or President of the German Reich established according to the constitution. The treaty also requires all clergy to abstain from working in and for political parties. Nazi breaches of the agreement began after it had been signed and intensified afterwards. The Church protested, including in the 1937 Mit brennender Sorge encyclical of Pope Pius XI. The Nazis planned to eliminate the Church's influence by restricting its organizations to purely religious activities.

The Reichskonkordat is the most controversial of several concordats that the Vatican negotiated during the pontificate of Pius XI. It is frequently discussed in works that deal with the rise of Adolf Hitler in the early 1930s and the Holocaust. The concordat has been described by some as giving moral legitimacy to the Nazi regime after Hitler had acquired quasi-dictatorial powers through the Enabling Act of 1933, an Act itself facilitated through the support of the Catholic Centre Party.

The treaty places constraints on the political activity of German clergy of the Catholic Church. With passage of the 1935 Nuremberg Laws, for example, a policy of nonintervention was followed. The majority of the German church hierarchy regarded the treaty as a symbol of peace between church and state. From a Catholic Church perspective, it has been argued that the Concordat prevented even greater evils being unleashed against the Church. Though some German bishops were unenthusiastic, and the Allies at the end of World War II felt it inappropriate, Pope Pius XII successfully argued to keep the concordat in force. It is still in force.

The 'Reichskonkordat' between Germany and the Holy See was signed on 20 July 1933 and ratified in 10 September of that year. The treaty was an extension of existing concordats already signed with Prussia and Bavaria. Concordats have been used to create binding agreements to safeguard church interests and its freedom to act, particularly in countries that do not have strong jurisprudence guaranteeing government non-interference in religious matters or where the church seeks a privileged position under government patronage.

Accounts of 20th-century diplomatic relations between Germany and the Vatican commonly take as their starting point the political scene in the late 19th century. German Chancellor Bismarck's Kulturkampf ("Battle for Culture") of 1871–1878 saw an attempt to influence a Protestant vision of nationalism over the new German Empire, and fused anticlericalism with suspicion of the Catholic population, whose loyalty was presumed to lie with Austria and France. The Catholic Centre Party had formed in 1870, initially to represent the religious interests of Catholics and Protestants, but was transformed by the Kulturkampf into the "political voice of Catholics". Bismarck's Culture Struggle was largely a failure.

Bismarck sought to restrict the power of the Catholic Church in Germany. He regarded the Roman Church as "the enemy within". His Kulturkampf included the disbanding of Catholic organizations, confiscation of church property, banishment or imprisonment of clergy, and an ongoing feud with the Vatican. According to novelist James Carroll, the end of Kulturkampf signaled "that the Church had successfully resisted to his face the man [Bismarck] who, according to an admiring Henry Kissinger, was 'outmaneuvered' by nobody." The Catholic Church's firm resistance to Bismarck and Kulturkampf, including passive resistance by the Church in general and the excommunication of collaborating priests, has been used as benchmark for assessing the Church's response to the Nazis from the early 1930s through World War II.

A formal realignment of Church and state relationships was considered desirable in the aftermath of the political instability of 1918 and the adoption of the Weimar constitution for the Reich along with the new constitutions in the German states in 1919. Key issues that the Church hoped to resolve related to state subsidies to the Church, support for Catholic schools, the appointment of bishops and the legal position of the clergy. The Reich government, in turn, wished for reasons of foreign policy to have friendly relations with the Holy See. Also, Germany wanted to prevent new diocesan boundaries from being established which would dilute Germany's ties to ceded German territories in the east such as Danzig and Upper Silesia.

Negotiations relating to specific points, rather than a general concordat, took place between 1919 and 1922. But even after subsequent feelers were put out between the two parties the negotiations failed, primarily because both the Reichstag and Reichsrat were dominated by non-Catholic majorities who, for a variety of reasons, did not want a formal pact with the Vatican. In the absence of an agreement relating to particular areas of concern with the Reich, the Holy See concluded more wide-ranging concordats with three German states where Catholics were concentrated: Bavaria (1924), Prussia (1929), and Baden (1932).