Adolf Georg Otto "Ago" von Maltzan, Baron zu Wartenberg und Penzlin (31 July 1877 – 23 September 1927) was a German diplomat during the Weimar Republic, serving as State Secretary of the Foreign Office and Ambassador in Washington.

Baron von Maltzan, who was usually called Ago based on the initials of his baptismal names,[1] was born on 31 July 1877 on his father's estate at Klein-Varchow, Mecklenburg, Germany.

[2] During World War I, von Maltzan served as First Lieutenant in the Mecklenburg Dragoons before he was transferred to diplomatic duty as representative of the Wilhelmstrasse (the Foreign Office) to the Commander-in-Chief Eastern Front in the Spring of 1917.

[2][6] In 1924, von Maltzan was appointed as the ambassador to the German Embassy in Washington but didn't present his credentials to President Calvin Coolidge at the White House until 12 March 1925.

In New York City, a memorial service was held for him at Zion Lutheran Church on the Upper East Side, which nearly 1,000 people attended including Julius P. Meyer, Rudolph Kessmeyer, Professor Theodor Wedepohl and Fritz Schroeder, and Karl von Lewinski among others.

[22] In 1927, Marquette University in Milwaukee, Wisconsin awarded him an honorary Doctorate of Law degree "on the basis of a long, distinguished professional career, and as an expression of international good-will.