Unusually for Africa, Rwanda is essentially a mono-linguistic state. The first language spoken in Rwanda is Kinyarwanda. In addition, most Rwandans speak a little of at least one international language.
Historically, French was the most widely recognised European language due to almost 50 years of Belgian colonisation. These days, English probably has the greater presence, partly because so many long-term exiles who returned after the genocide were educated in Uganda, Kenya, or Tanzania. English also partly replaced French as the international language of education in 2009.
In rural areas, KiSwahili, a coastal Bantu language that has come to serve as the lingua franca of East Africa, is still more widely understood than either English or French.
From a visitor’s perspective, it’s pretty easy to get around in either English or French, both of which are recognised as an official language alongside Kinyarwanda. But English is undoubtedly the primary language of the tourist industry.