Kongo-Saharan is a hypothetical language family proposed by Edgar Gregersen (1972) that unites the Niger-Congo and Nilo-Saharan families of Africa. However, Blench (1992) suggests that, if related, Niger-Congo might instead be a branch within Nilo-Saharan, closest to the Central Sudanic languages, not coordinate with it. He calls his proposal Niger-Saharan.
Roger Blench. "Is Niger-Congo simply a branch of Nilo-Saharan?", in ed. Nicolai & Rottland, Fifth Nilo-Saharan Linguistics Colloquium. Nice, 24-29 August1992. Proceedings. (Nilo-Saharan 10). Koeln: Koeppe Verlag. 1995. pp.36-49.
Edgar Gregersen. "Kongo-Saharan". Journal of African Languages, 11, 1:69-89. 1972.