He made the announcement in a televised address to the nation.
Jacob Zuma , who has been in power since 2009, faces numerous allegations of corruption.
He was under increasing pressure to give way to Deputy President Cyril Ramaphosa, who is the ANC's new leader.
Earlier on Wednesday, police swooped on the Johannesburg home of the powerful and wealthy Gupta family with whom Mr Zuma has close ties.(BBC/AP)