Greeks are voting in a general election which could result in Greece trying to renegotiate the terms of its bailout with international lenders.
The leader of the left-wing Syriza party, Alexis Tsipras, has pledged to write off Greece’s huge debt and revoke austerity measures.
However, the current conservative prime minister, Antonis Samaras, says the austerity measures are working.
He has urged voters not to take Greece to the brink of catastrophe.
Greece has endured tough budget cuts in return for its bailout, negotiated with the European Union, International Monetary Fund (IMF) and European Central Bank (ECB).
The economy has shrunk drastically since the 2008 global financial crisis, and increasing unemployment has thrown many Greeks into poverty.
Polls across Greece opened at 07:00 local time (05:00 GMT) and will close at 19:00.
There are nearly 10 million eligible voters, who are electing the country’s 300-member parliament.
The first exit polls are expected immediately after the voting ends.