Robert Butler (1897-1955) was the United States Ambassador to Australia (1946–48) and Cuba (1948–1951). He died of a heart attack on September 15, 1955. Butler was born in St. Paul, Minnesota and his wife was Margaret Porter. During World War II he was active in shipbuilding. He was the president of Walter Butler Shipbuilders Inc. and Walter Butler Shipbuilding-Duluth which built a number of cargo ships in Duluth, Minnesota and Superior, Wisconsin during the war. According to a former aide, Butler had been the focus of an assassination plot during his term as Ambassador to Cuba.