Mr Ramaphosa, the country’s fourth democratically elected president since the end of apartheid, took the presidential oath in a packed Loftus Versfeld stadium in capital Pretoria.
“Today our nation enters a new era of hope and renewal,” said the 66-year-old, flanked by foreign leaders including Congolese President Felix Tshisekedi and Chinese Premier Li Keqiang.
“They can be solved and I stand here to say they are going to be solved,” he added.
Mr Ramaphosa’s African National Congress (ANC) clinched a 57.5% majority in a general election earlier this month, down from 62% in 2014, as voters turned against the ruling party due to revelations about government corruption and record unemployment.
The former anti-apartheid activist narrowly won the ANC leadership race in late 2017 and replaced scandal-plagued predecessor Jacob Zuma as state president in February 2018, a year before the latter’s term was due to expire.
There was no sign at Saturday’s ceremony of Mr Zuma, who has insisted he did nothing wrong and that allegations are politically motivated.
Mr Ramaphosa struggled to mend factions in the party opposed to his reform plans, especially at cash-strapped state power supplier Eskom.
His promises to punish party members accused of corruption have also stuttered.
Meanwhile, South Africa’s economy is set for a first-quarter contraction after mining and manufacturing weakened, prompting the central bank to cut its 2019 growth forecast to 1%, well below the rate of at least 3% needed to bring down debt, budget deficits and joblessness.
