He was speaking at the African Union's headquarters in Ethiopia's capital, Addis Ababa, the first time a sitting US president has addressed the body.
Earlier in the trip, President Obama visited Kenya, the homeland of his late father where he met his relatives. President Obama specifically mentioned Burundi, whose president Pierre Nkurunziza has controversially been re-elected for a third term.
According to BBC, the US President has called on the African Union to ensure leaders respect their constitutions and step down when their term ends.
He said democracy was about more than just holding elections. His address to the AU marks the end of his five-day visit to Africa.
The trip has focused heavily on trade and security.