Excommunicated Nazis?

In 1931, the bishop of Mainz excommunicated all Nazis in his diocese. Shortly thereafter, the German bishops met together and applied the excommunication across the country to leaders and active members of the party, and those displaying Nazi symbols or actively promoting them. When the Nazi leadership appealed to the Vatican, their appeal was rejected.

Hitler was raised by a Catholic mother and an atheist father. His mother had him baptized as an infant, but even as a young teen he expressed disgust for the Church and only went to church when his mother forced him. He embraced his father's atheism and rejected the Church as an apostate before he was even 18.

So, either we respect his own religious identity, and he apostatized (rejected Christianity altogether) sometime around 1904-07, or we ignore it and consider him excommunicated with the rest in 1931. Even before that there were repeated declarations that the Nazis were incompatible with Catholic teaching and morality, and were eventually described by the Church as pantheist and pagan, in addition to being racist and immoral.

NB: there's no such thing as a posthumous excommunication. Someone's teaching can be condemned, or actions they took condemned, posthumously, but not excommunication. Hitler died having been out of the Church for forty years, his entire adult life.

Have any members of the Nazi party under Adolf Hitler (including Hitler) ever been excommunicated from the Catholic Church?

Hitler may not have been named, but yes he was excommunicated from the Catholic Church, for he was an active member of the Nazi Party.

February 1931, the German bishops meeting in conferences in Fulda and Freising supported the action of the bishop of Mainz, but limited the excommunications to Nazi leaders and activists.

In early 1931, the German bishops excommunicated the Nazi leadership and banned Catholics from the party. Although the ban was modified in the spring of 1933 due to a law requiring all civil servants and union members to be party members, the condemnation of core Nazi ideology continued. See: The Churches and the Third Reich. 2 vols. Fortress Press, 1988 pp. 150–162.

In February 1931, the German bishops excommunicated all active Nazi party members. This included Hitler. This penalty was not imposed on those who merely voted Nazi. It was hoped to persuade them by argument. The same policy was in operation against the Communists. - The Catholic Response to Nazism

This excommunication was well before World War II broke out or the Nazi’s final solution was underway.

Let us set the stage shall we:

From the very beginning the Nazis had mixed attitudes toward the Catholic Church. Adolf Hitler, a nominal Catholic, was tolerant of Catholicism. Many other Nazis were practising Catholics. A staunch Catholic and early Nazi patron who will appear later in this study was General Franz Ritter von Epp. He commanded one of the military groups which liberated Munich from Soviet rule in May, 1919. Immediately afterward he ordered a Mass of thanksgiving, for which act of piety he was dubbed by the impious as the "Virgin Mary General" (Muttergottesgeneral).

Besides being opposed to what they called the red international of socialism and the golden international of Judaism, many Nazis were also opposed to the black international of Catholicism. Anti-Catholics among the early Nazis included the leading Nazi philosopher and writer, Alfred Rosenberg, and Hermann Esser, who before he was of age became one of Hitler's most effective speakers. Heinrich Himmler, who joined the National Socialist Party in 1925, was another anti-Catholic who was to become a leading Nazi.

Because of this anti-Catholic aspect of National Socialism, because it made race a kind of religion, because it stressed German nationalism while Catholics were often separatists, and because Nazis attacked the specifically Catholic political parties, there were important religious and political differences between Nazism and Catholicism in the 1920's. After the spectacular success of the National Socialist Party in the elections to the Reichstag in the summer of 1930, Catholic bishops in Germany began forbidding Catholics to be members of the National Socialist Party. By March of 1931 all the German bishops had condemned National Socialism, and some bishops instructed Catholics not to vote for the National Socialist Party in the crucial elections during 1932 and on March 5, 1933. The eight bishops of Bavaria issued on February 12, 1931, a declaration which listed five false doctrines of Nazism : 1) it puts race before religion, 2) it rejects Old Testament revelation, 3) it denies the primacy of the Pope because he represents an authority outside Germany, 4) it plans an undogmatic National German Church, and 5) it sets up the moral feeling of the German race as the criterion of Christian morality, which, however, is essentially universal. Priests were forbidden to belong to the National Socialist Party and were instructed to refuse the sacraments to active members. - The Formulation of Nazi Policy towards the Catholic Church in Bavaria from 1933 to 1936

For further details please feel free to parse the following article(s):

• The response of the German bishops to the Reichskonkordat