Polls for Turkey's landmark elections will open at 8am local time (05:00 GMT) and close at 5pm local time (14:00 GMT). The winner will assume vast new presidential powers.
Candidates have held their final rallies.
President Recep Tayyip Erdogan has urged people to get out and vote. He attacked his opposition for lacking vision, and boasted of his achievements in office - such as new infrastructure and improved healthcare.
His main challenger, Muharrem Ince, also held a rally in Istanbul. He painted a bleak picture of Turkey under Erdogan, saying its currency would remain weak, and its refugee problems unresolved.
Six candidates are running for president.
Al Jazeera's Sinem Koseoglu takes a look at the frontrunners.