The country's deputy president defeated former cabinet minister Nkosazana Dlamini-Zuma, Zuma's ex-wife, after a marathon voting process.
Ramaphosa is in a strong position to become president in 2019 polls, says a BBC report.
The leadership battle caused fierce political infighting, raising fears the party might split before the election.
Almost 5,000 delegates voted in an internal party election at a conference centre in Johannesburg. Ramaphosa won with 2,440 votes to 2,261 for his rival Dlamini-Zuma, according to the guardian.
The result triggered celebrations among party delegates in Johannesburg and also on the streets of the city.
Media reports said earlier that the announcement had been delayed, with Dlamini-Zuma's camp demanding a recount.
The voting process started on Sunday.
