Buhari died on Sunday in London, where he had been cared for in recent weeks. He was elected president in 2015 and ruled the country until 2023, when he was succeeded by party colleague Bola Tinubu.
Buhari ruled the country as a military leader in 1983–1985 before he became a "converted democrat". He replaced Goodluck Jonathan in the presidential election in 2015 by promising to combat the Islamist terrorist group Boko Haram and combat corruption.
When he won the first presidential election, it was seen as an opportunity to change course for the country. But during his time in power, he failed to stop corruption and violence.
Nigeria has around 227 million inhabitants and is Africa's largest economy.