Namibia's outgoing president, Hifikepunye Pohamba, has won the Mo Ibrahim Foundation's $5m African leadership prize, an award meant to recognise good governance that has been presented only three times in eight years.
Since it was set up by the Sudanese telecom tycoon in 2007, the prize has gone to three former presidents, from Cape Verde, Mozambique and Botswana. In other years, no one was found to have met the criteria.
To win the prize, a leader must have been democratically elected and have left office in the last three years, serving only their constitutionally mandated term. The winner must also have displayed "exceptional leadership".
Although elections have now become common on a continent once better known for military coups and instability, some leaders have stayed in office long after their original mandate, often pushing through constitutional changes to hold to power.
Announcing the award in Nairobi, the Mo Ibrahim committee praised Pohamba's commitment to the rule of law and his respect for the constitution, as well as his promotion of gender equality.
Pohamba, aged 79, was first elected president in 2005 and is due to step down this month. The elections held under his leadership were considered by observers to be free and fair.
Pohamba was a founding member of the now ruling South West African People's Organisation (Swapo), playing a central role in decades of struggle for independence from South Africa.
He was imprisoned in the 1960s for political activism but continued to fight against South Africa's apartheid government until the end of white-minority rule in 1994.
He held home affairs and marine resources portfolios in cabinet prior to becoming president.
The winner receives $5m, given over 10 years, and after that receives $200 000 a year for life.
The previous recipients were former presidents Pedro de Verona Rogrigues Pires of Cape Verde, Mozambique's Joaquim Chissano and Festus Mogae of Botswana. South Africa's Nelson Mandela was also given an honorary award.