Roo·se·velt (rō'zə-vělt', rōz'vělt', -vəlt, rōō'-) American diplomat, writer, and First Lady of the United States (1933-1945) as the wife of President Franklin D. Roosevelt. A delegate to the United Nations (1945-1952 and 1961-1962), she was an outspoken advocate of human rights. Her written works include This I Remember (1949).