Carl-Ludwig Diego von Bergen (1872 – 7 October 1944) was the ambassador to the Holy See from the Kingdom of Prussia (1915–1918), the Weimar Republic (1920–1933), and Nazi Germany (1933–1943), most notably during the negotiation of the Reichskonkordat and during the Second World War.
From 1930 to 1943, by virtue of seniority, Bergen was also the doyen of the diplomatic corps accredited to the Holy See. This office entitled him to speak at the funeral of Pope Pius XI in 1939, when he urged the cardinals to elect a new pope who would work with the fascist governments of Europe to build "a new world upon the ruins of a past that in many things has no longer any reason to exist". Bergen was recalled in 1943, aged more than seventy, which was a good deal more than the mandatory retirement age for German diplomats, and was replaced by Ernst von Weizsäcker.