Isaac Kalonji Mutambayi (9 September 1915 – 3 August 2009) was a Congolese Protestant minister and statesman who served as the President of the Senate of the Democratic Republic of the Congo from 1962 until 1965.

However, later that year the Italian merchant running the enterprise repatriated himself due to the development of World War II, and Kalonji lost his job.

[3] In September 1958 Kalonji led several other Baluba in creating the Fédération des Association de Ressortissments du Kasai au Katanga (FEDEKA) to oppose the Confédération des associations tribales du Katanga (CONAKAT)'s perceived anti-Baluba bias[5] and politically mobilise Katangese residents of Kasian origins.

[6] Kalonji served as a delegate for the Katanga Cartel (an alliance between FEDEKA, BALUBAKAT, and ATCAR) at the Belgo-Congolese Round Table Conference in early 1960.

[9] As the country fell into crisis, Kalonji's position in national politics became tenuous due to his mixed ethnicity and the fact that he adhered to Lumumba's beliefs.

[11] In October he was made a member of a commission assembled by Lumumba (then deposed) tasked with managing his relations with the United Nations Operation in the Congo.

That year he played a significant role in attempting to reconcile the Luba and Lulua tribes and attended the Eurafrican Interparliamentary Conference of Strasbourg on the Association of African Countries in the Common Market.