Baron Émile-Ernest de Cartier de Marchienne (30 November 1871 – 10 May 1946) was a Belgian diplomat who was ambassador to a number of countries, most principally the United States and the United Kingdom.

[3] From 1910 to 1917, he served as Envoy Extraordinary and Minister Plenipotentiary in Peking, China and Siam.

From 1917 to 1927,[4] he was head of the Belgian legation in Washington, D.C. (which was elevated to an embassy in 1919), while also serving as Envoy Extraordinary and Minister Plenipotentiary in Cuba, Haiti and the Dominican Republic from 1926 to 1927.

[5][6] From 1927 until his death in 1946, which included all of World War II, he was the Belgian Ambassador to the United Kingdom, of which the last six he was Dean of the Diplomatic Corps.

[9][15][16] The Baroness died on 18 February 1936,[17] leaving a net estate worth $685,026.