The violent response to the announcement has stirred memories of a brief civil war that erupted after then president Laurent Gbagbo refused to cede to Ouattara after elections in 2010.
Here is a timeline of this key period in the runup to the October 31 poll:
Ouattara steps aside
On March 5, 2020, Ouattara, 78, announces he will not run for a third term in order to make way for "the younger generation", ending months of speculation over whether he would seek another mandate.
Coulibaly steps in
In mid-March, Prime Minister Amadou Gon Coulibaly is nominated as the ruling RHDP party's candidate.
Only July 8 Coulibaly dies unexpectedly from a heart attack, plunging the country into uncertainty.
Ouattara will run
On August 6, Ouattara finally announces he will seek re-election in October.
The opposition slam the decision, saying it is against the constitution, which allows two terms, but Ouattara and his supporters argue that a 2016 constitutional tweak reset the clock.
Protests and violence
Ouattara's announcement triggers protests that turn violent, leaving around 15 people dead.
On August 22 Ouattara is formally chosen by his party to run for a third term.
Gbagbo and Soro candidates
On September 3 Gbagbo as well as former rebel leader turned prime minister Guillaume Soro also file their candidacies.
The ex-president Henri Konan Bedie, 86, is officially nominated as candidate for his party on September 12.
Validated and rejected
On September 14, the Constitutional Council, the country's top court, authorises only four candidacies out of 40 applications it receiveds. It validates Ouattara's bid but bars Gbagbo and Soro.