Guillermo Sevilla Sacasa (September 11, 1908, Leon, Nicaragua – December 16, 1997 Potomac, Maryland, United States ) was the Nicaraguan ambassador to the United States from 1943 until July 19, 1979, when President Anastasio Somoza Debayle was forced into exile following the Nicaraguan Revolution. As a result of his record-breaking service as ambassador in Washington, D.C., he was appointed Dean of the Diplomatic Corps, a position he held from January 1958 to July 1979.