The Kingdom of Roumania ( or ` Romania ' after 1969 ) was the old Romanian state based on a form of parliamentary monarchy between 13 March 1881 and 30 December 1947 , specified by the First ( in 1866 ) , and respectively , the Second Constitution of Roumania . The Kingdom of Romania was the Romanian state based on a form of parliamentary monarchy between 13 March 1881 and 30 December 1947 , specified by the first three Constitutions of Romania ( 1866 , 1923 , 1938 ) .