In his first major speech after Zumas bruising nine-year term ended, Ramaphosa outlined a grand vision to revive the stagnant economy, address dire unemployment and control spiralling government debt.
"We should put all the negativity that has dogged our country behind us because a new dawn is upon us and a wonderful dawn has arrived," Ramaphosa told parliament in the annual State of the Nation address.
"Tough decisions have to be made to close our fiscal gap, stabilise our debt and restore our state-owned enterprises to health," he said, adding "our most grave and most pressing challenge is youth unemployment."
Zuma was forced to resign on Wednesday after the African National Congress party finally turned against him, with pro-business reformist Ramaphosa sworn in as president only on Thursday.
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After multiple corruption scandals, economic slowdown and falling popularity with voters, the ANC had threatened to oust Zuma via a no-confidence vote in parliament.
Zuma resigned reluctantly, complaining he had received "very unfair" treatment from the party.
Ramaphosa, 65, is a former trade unionist who led talks to end apartheid in the early 1990s and then became a multi-millionaire businessman before returning to politics.