Liberians are to choose a new president in a run-off vote between Vice-President Joseph Boakai and former international footballer George Weah, today December 26.
Mr Weah, 51, won the first round, but did not secure the required 50% of the vote for an outright victory.
The second round of voting to succeed Ellen Johnson Sirleaf was delayed because of legal challenges.
Liberia, which was founded by freed US slaves in the 19th Century, has not had a smooth transfer of power in 73 years.
Polls across Liberia will open at 08:00 GMT and close at 18:00 GMT.
More than two million people are eligible to cast their ballots.