Almost 5.5 million registered voters can vote at roughly 15,000 polling stations. Results are expected within 24 hours after voting closes at 18:00 GMT.
A candidate needs to secure more than 50 percent of the vote to win.
Twelve candidates will be vying for the highest office, but only the incumbent, Alpha Conde, and Cellou Dalein Diallo, 68, the leader of main opposition party Union of Democratic Forces of Guinea (UFDG), are said to be in with a chance of victory.
Al Jazeera’s Nicolas Haque reports.
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