Emperor Haile Selassie signs the first constitution of Ethiopia.

The emperor of Ethiopia, also known as the Atse, was the hereditary ruler of the Ethiopian Empire, from at least the 13th century until the abolition of the monarchy in 1975. The emperor was the head of state and head of government, with ultimate executive, judicial and legislative power in that country. A National Geographic article from 1965 called Imperial Ethiopia "nominally a constitutional monarchy; in fact it was a benevolent autocracy".

Haile Selassie I was Emperor of Ethiopia from 1930 to 1974. He rose to power as the Regent Plenipotentiary of Ethiopia under Empress Zewditu between 1916 and 1930.

The 1931 Constitution of Ethiopia was the first modern constitution of the Ethiopian Empire, intended to officially replace the Fetha Nagast, which had been the supreme law since the Middle Ages. It was promulgated in "an impressive ceremony" held 16 July 1931 in the presence of Emperor Haile Selassie, who had long desired to proclaim one for his country. In the preface to his translation of this constitution into English, William Stern writes, "this was the first instance in history where an absolute ruler had sought voluntarily to share sovereign power with the subjects of his realm." This statement, however, is not completely accurate, as the adoption of a constitution was somewhat pressed by international opinion.