South Koreans are voting in a presidential election, called early after a huge corruption scandal brought down their former leader.
Left-leaning Moon Jae-in is the clear front-runner with centrist Ahn Cheol-soo his nearest challenger.
The election is being closely watched at a time of economic uncertainty and heightened tensions with North Korea.
Moon wants to increase contact with the North in contrast to ex-leader Park Geun-hye who cut almost all ties.
On the final day of campaigning, Moon called for an “overwhelming victory”, saying it would help to heal a national divide caused by the downfall and impeachment of conservative Park.
Ahn, campaigning in swing states, said he was still confident he could win.