Rwandas Democratic Green party president
"I have accepted your request to represent you as the presidential candidate for the upcoming presidential election which will takes place on 4th August 2017," Habineza said after a meeting of party leaders in Kigali.
Only incumbent Paul Kagame, who has been in power since 1994, had previously come forward as a candidate.
A constitutional amendment passed this year means Kagame -- in charge since taking power at the head of a rebel army 22 years ago -- is able to stand for re-election for another seven-year term.
"We want to bring democracy to this country" Habineza told reporters.
"Democracy does not come from the sky, it won't come from America or Europe, we are the ones who have to fight for it"
Rwanda is regularly praised for its stability and economic performance but criticised for a lack of political freedoms.
Several opposition parties -- including the United Democratic Forces (FDU) -- are not officially recognised and cannot participate in elections.
FDU leader Victoire Ingabire was arrested in 2010 while campaigning against Kagame.