Media reports earlier said the announcement had been delayed after Ms Dlamini-Zuma's camp had demanded a recount.
Mr Ramaphosa is widely expected to become president after 2019 elections.
Mr Ramaphosa was widely considered the sensible choice in the election.
"South Africa's chance for huge change is here and Ramaphosa is in a position now to prove to the electorate and to investors that he can bring that change", said Simon Quijano-Evans, strategist at Legal & General Investment Management in London.
In June the ANC welcomed an investigation by South Africa's anti-corruption watchdog into several allies of Zuma allegedly linked to corruption at three state-owned companies. He is viewed positively by investors and markets for his potential as a reformer, though NDZ had promised "radical economic transformation".
Following the news of his election, the rand extended gains to climb 4% against the dollar, the biggest jump in two years to its strongest level since March.
NY woman charged with sending $85000 in Bitcoin to support Isil
The DOJ identified the woman as 27-year-old Zoobia Shahnaz, who was born in Pakistan and worked as a lab technician in the U.S. If convicted on all charges, Shahnaz could be sentenced to as many as 90 years in prison, according to the attorney's office.
Outgoing President Zuma's second and final term as party leader has ended after a scandal-ridden tenure that has seen a plummet in the popularity of Mandela's liberation movement.
Ramaphosa is a businessman and former trade union leader, and also one of South Africa's richest men.
The vote was a long and acrimonious process.
A victor had been expected to be announced on Sunday, but owing to long delays, the vote had been pushed back repeatedly.
The leadership battle caused fierce political infighting, raising fears the party may split before the election.
Mr Ramaphosa will have to take tough decisions to restore investor confidence and will confront a number of obstacles that will make it hard to resuscitate the economy, according to Ben Payton, head of Africa Research at Verisk Maplecroft, a Bath, England-based risk-advisory company.
The mood at the party conclave, held once every five years, was jubilant on Saturday as delegates arrived at a conference center in luxury buses, clad in the ANC's yellow and green colors.