Ramphele made the announcement at a Foreign Correspondent's Association of South Africa (FCA) meeting on Thursday.
Agang was formed as a party political platform in February, but will now become an official political party.
"We are supposed to get our registration certificate this week," the struggle icon and organisation leader said.
She elaborated on the nature of Agang, stating that "it doesn't make sense to talk about left-right. What Agang stands for is social justice." She also said she believes "we [Agang] have a chance to gain enough votes to form an alternative government".
Ramphele criticised President Jacob Zuma's adversarial stance towards opposition parties: "Jacob Zuma's attitude to opposition parties is part of liberation culture. 'You're either with us or against us.' Not surprised."
Analysts, the Democratic Alliance (DA) and the ANC said Ramphele would struggle to provide a viable alternative to the current political status quo if she intended to form a political party.
Media reports suggested last year that Ramphele would be joining the DA as a replacement for incumbent leader Helen Zille and Zille tried to get Ramphele to join her party last year,but she declined and formed the Citizens' Movement, a nongovernmental organisation. She said at the time that she had never joined a political party in her life.
Ramphele on Thursday spoke candidly about the state of South Africa’s democracy, schools and healthcare: