The Founder and Executive Chairman, Famfa Oil Limited, Folorunsho Alakija, whose net worth dropped to $1.1 billion from $1.3 billion also ranked on the list.
The worldwide magazine also listed Mike Adenuga, Chairman/Chief Executive Officer of Globacom who has interests in investments in oil and gas, real estate and other concerns moved up to become the second richest man in Africa.
Among the few on the list who are richer than a year ago was Strive Masiyiwa of Zimbabwe, worth an estimated $2.3 billion, up from $1.6 billion last year.
Forbes blamed plunging stock values and weaker currencies for the shrinking in the billionaires club in Africa.
The United States (U.S.) magazine said Adenuga's net worth increased tremendously from $5.3 billion to $9.2 billion because he provided more detailed information about his assets. His grandfather founded diamond mining firm DeBeers, which Nicky ran and then sold to mining giant Anglo American for $5.1 billion cash in 2012.
The eighth slot had five persons with one of them being Isabel dos Santos, Africa's richest woman whose wealth is estimated at $2.3 billion.
The other three are Koos Bekker with a net worth of $2.3 billion.
The rank was a tie with South African banker, Michiel Le Roux.
Aliko Dangote, President and Chief Executive Officer, Dangote Group, Nigeria, during the African Fellowship Programe with Young Global Leaders announcement at the World Economic Forum on Africa 2011 held in Cape Town, South Africa, 4-6 May 2011. Her net worth dropped due a decline in the value of the oil field, in part because its production has levelled off.
Forbes, in its remarks on the reduced net worth of the featured personalities, linked it to plunging stock prices and weaker currencies. However, the average net worth for each list member this year has climbed to $3.4 billion from $3.3 billion in early 2018.
Mike Adenuga was one of the only billionaire that became richer past year and he neither pays tithes nor gives first fruit. All but four members of the list have smaller fortunes than a year ago.
He is followed closely - if one can use that word when discussing billions - by Nigeria's Mike Adenuga, the founder of Globacom and Conoil Producing.
Those who didn't make the billionaire cut this year include Aspen Pharmacare founder Stephen Saad, Assor Group's Desmond Sacco and Shoprite investor Christoffel Wiese.