Rejecting European creditors' demands, Greeks voted against the terms of a bailout on Sunday, delivering one of the biggest blows to Europe's drive to forge an enduring monetary union since the euro was launched in 1999.
The Australian dollar dropped to a six-year low of 74.52 US cents before recovering slightly in the wake of referendum result.
At 10.06am (AEST), the local unit was trading at US74.98c, down from US75.84c on Friday.
The local currency dipped below US74.52c in early morning trade, its lowest level since May 2009.
With 87 per cent of ballots counted, more than 60 per cent of Greeks had voted ‘No’ in the controversial referendum that may trigger the country’s exit from the eurozone.
ANZ senior FX manager Sam Tuck said markets had adopted a risk-averse sentiment, and investors today would be watching for the European response.
Germany and France are calling for a special summit of eurozone leaders, as a Greek failure to reach a deal with it’s creditors could trigger the country’s exit from the eurozone.
“They’ve been very clear last week that a ‘No’ vote would not strengthen the Greek negotiating position, so they’ve got a very tough choice in front of them,” he said.
Mr Tuck said the Greek central bank had also put in a request to the European Central Bank to increase the emergency lending authority.
“That’s the only thing keeping banks afloat at the moment, so it’s going to be very interesting to see what the ECB says on that front,” he said.
The referendum result also prompted a fall in the euro against the US.
One euro was worth $US1.0987 at 5.15am (AEST), down 1.20 per cent from Friday night, in electronic trading before Asian markets opened.
Australian shares open sharply lower
Over $30 billion has been wiped off the Australian stock market in response to Greece's referendum. (AAP)
The ASX/S&P 200 and All Ordinaries fell by 1.7 per cent in early Monday trade in response to the resounding `No' vote to the austerity measures, which many see as a vote against the country's membership in the euro zone.
Greeks delivered a stunning rebuke to Europe at the highly-anticipated referendum overnight, with 61 per cent backing the `No' campaign advocated by the ruling Syriza campaign.
The move caught markets by surprise and significantly increased expectations Greece would leave or be forced out of the euro zone.
'2 in 3 chance' of Grexit
Investment bank JP Morgan now says there is a two-in-three chance of the country leaving the euro zone.
"This is a path that suggests to us that there is now a high likelihood of Greek exit from the euro, and possibly under chaotic circumstances," it said in a research note.
Every sector of the Australian market was deep in negative territory, with the exception of gold miners.
Gold tends to do well during times of uncertainty due to the metal's reputation as a "safe haven" asset.
IG Market strategist Evan Lucas said the market sell off would be considerably worse if not for expectations that Chinese stocks will rally following the announcement of new emergency measures.
The country has moved to prop up its ailing share market, which has lost 26 per cent in the past fortnight, by suspending new listings and enlisting the help of its top stock brokers, which have agreed to collectively buy at least 120 billion yuan ($A25.56 billion) of shares.
"Clearly China has got every reason to have a positive day today, if it is not supported today then we've got some serious problems," he said.
