Saakashvili ousted Eduard Shevardnadze in a revolution on pledges to restore stability and prosperity to the ex-Soviet state.
Sunday’s election, called swiftly after Shevardnadze resigned in November, is under scrutiny by the West and neighbouring power Russia, both keen to cement their influence in a country seen as a vital transit link between the Middle East and Europe.
It is also a chance for Georgia, a volatile Caucasus country which was torn by civil war and separatism after the 1991 Soviet collapse, to prove its democratic credentials after rights groups criticised last year's parliamentary poll for fraud.
Polling stations in Georgia's 75 districts open at 04:00 GMT and close 12 hours later.
High voter turn-out needed
Saakashvili needs 50% plus one vote to avoid a runoff and win outright to crown a successful drive for the presidency that started when he led thousands on the streets to oust his former mentor and ex-Soviet foreign minister Shevardnadze.
"Of course I will vote for Saakashvili," Tea Guchmazashvili, an engineer-turned-housewife, said. "We all know that America stands behind Saakashvili, and that could be a good thing if they help the people... This is the only chance for the people."
Georgia's Mikhail Saakashvili is
facing little competition
Fighting on an anti-corruption platform, the only threat to Saakashvili's all-but-ensured win is a low turnout following the New Year's holiday. On Saturday Saakashvili and election officials called on Georgians to turn out en masse.
"If not enough voters turn out to vote it is not just a legal danger but a political threat to stability," Central Election Commission chief Zurab Chiaberashvili told reporters. "I hope that voter activity will save these elections from failure."
Facing little competition from five other candidates - three lawyers, a former regional governor and the head of an organisation for the disabled - Saakashvili has vowed to use his victory to crack down on corruption, open up markets to investors and restore central control over Georgia's restive regions.
A smooth election would also allow the country to reap the benefits from a US-backed $2.7 billion pipeline due to take Caspian oil across Georgia to Western markets in 2005, the 36-year-old lawyer said.
But the poll has been overshadowed by violence and a battle with the restive regions over whether they would participate in the vote.
A grenade attack on 29 December on the headquarters of an independent television station that played a key role in Shevardnadze's downfall was the latest in a string of attacks in the capital Tbilisi.
The Black Sea region of Abkhazia will boycott the event, but Saakashvili said parts of wayward South Ossetia would take part.