Ouattara is heavily favoured to win Sunday's ballot, meant to draw a line under a decade-long crisis which ended in a brief 2011 civil war that killed over 3,000 people in the wake of the last presidential vote.
The president wrapped up his campaign on Friday cheered by thousands of supporters during a tour of the economic capital Abidjan ahead of a closing rally in the central Place de la Republic of the Plateau business district.
Banny is the third of 10 candidates to pull out of the race.
"After carrying through to the end the fight to push our leaders to spare Ivory Coast from renewed suffering, I have decided to withdraw from this unfair process," he told a news conference.
Mamadou Koulibaly and Amara Essy, both members of the opposition National Coalition for Change to which Banny also belongs, have also withdrawn claiming the election process was unfairly stacked in Ouattara's favour. They are calling for a boycott.
Earlier this week, Banny alleged that there were irregularities on the voter lists that could allow some voters to cast multiple ballots.
The West African nation's elections commission denied the claim and said Banny had failed to respond when it asked him to present evidence of the allegation.
Since taking the helm of francophone West Africa's largest economy, Ouattara - a former senior International Monetary Fund official - has overseen a strong recovery that has attracted investors and turned Ivory Coast into one of Africa's economic stars.
Growth has averaged around 9 percent over the past three years, but many ordinary Ivorians say they have yet to feel the benefits of the boom.