He admitted that he had not been “the epitome of perfection”, and that he did not fear leaving political office.
The ruling African National Congress party instructed Zuma to resign and threatened its lawmakers would vote to sack him via a no-confidence vote in parliament scheduled for Thursday if he did not resign beforehand.
They cited President Zuma’s “unreasonable, irrational and reckless” behaviour, which they said was a threat to state security and a danger to society.
The South African Parliament will now elect Mr Zuma’s replacement.
It’s almost certain ANC Leader and Deputy President Cyril Ramaphosa, 65, will be elected, due to the party’s dominance in parliament.
Ramaphosa defeated Zuma’s ex-wife to become leader of the party in an election held in December.
In a televised speech to the nation, Mr Zuma said: “I fear no motion of no confidence nor impeachment, for they are the lawful mechanisms for the people of this beautiful country to remove their presidents.
He added: “I have served the people of South Africa to the best of my ability. I am forever grateful that they trusted me with their highest office in the land. But when I accepted the deployment I understood and undertook to subject myself to the supreme law of the land: The constitution.
Zuma said earlier on Wednesday that the ANC, which has called for him to step down, had not told him what he had done wrong.
In a television interview earlier, Zuma derided the decision and said he had been “victimised” by the party.