Robert Granville Caldwell (1882–1976) was an American historian, author, and diplomat who served as Envoy Extraordinary and Minister Plenipotentiary of the United States to Portugal and to Bolivia, and held teaching posts at Rice University, MIT, and other institutions.

[1][2] He studied at the College of Wooster, from which he graduated summa cum laude in 1904 and was elected to Phi Beta Kappa.

[1] Caldwell was appointed the chief representative of the United States to Portugal, at the rank of Envoy Extraordinary and Minister Plenipotentiary, on June 13, 1933, presenting his credentials on August 21, 1933, and serving until May 28, 1937.

[3] Following his return to the United States, Caldwell accepted an appointment as dean of humanities at the Massachusetts Institute of Technology, a post he held until 1948.

[1] Caldwell was the author of three books: The Lopez Expedition to Cuba (1915), A Short History of the American People (1927), and James A. Garfield — Party Chieftain (1931).