What is the most widely spoken language on the continent of Africa?

Arabic is the most widely spoken language in Afica.

Answer

Swahili is most widely spoken African language. Swahili is spoken in these countries: Tanzania 99%, Kenya 87%, Uganda 85%, Burundi 55%, Democratic Republic of the Congo 48%, Rwanda 28%, Swahili is also spoken in southern Somalia, Ethiopia and Sudan and northern Mozambique and the Comoros Islands. It has more than 11 million native speakers (speak Swahili as first language) and more than 120 million secondary speakers. That makes Swahili the largest African language.

Answer

Arabic is widely spoken in many African countries, but it is naturally not counted as one of African languages even though there's arabic-africans lives in Africa; it is because most of native African countries has a low percentage of Arabic speakers. [Note: This is in error. Arabic is an Afro-Asiatic language, and therefore qualifies as a native language of Africa.]