The Belgian Congo, also known as the Congo Free State or Congo-Leopoldville, was a former colony under the reign of King Leopold II of Belgium from 1885 to 1908. The word "Congo" itself is often used to refer to the territory during that time. Other synonyms include "Democratic Republic of Congo," "Republic of Congo," and "Zaire," which was adopted from 1971 to 1997. However, it's essential to note that these names refer to the Congo's current status and territory, rather than its former colonial past under Belgium. As such, when discussing the Belgian Congo's history, it's accurate to refer to it specifically as the Belgian Congo.