Victorian Premier Daniel Andrews has confirmed masks will be mandatory for all Victorians from Sunday 11.59.
It comes as 723 new cases of COVID-19 were detected in the past 24 hours.
13 people died of coronavirus in that time, bringing the total to 105.
Mr Andrews said from 11.59pm on Sunday night, every regional Victorian must wear a mask when out of their home.
"It's something we can do in regional Victoria without causing economic cost but.. while getting significant health benefit," he said.
"I don't think this is the biggest leap."
Mr Andrews said many people in regional Victoria were already wearing masks.
"We have low numbers in regional Victoria and we want to jealously guard that," he said.
Mr Andrews said while most cases were in metro areas, there had been a significant jump in regional communities.
"It's vital we stop this virus further seeping into regional Victoria," he said.
"Last week, and based on the latest in scientific study, we announced that face coverings would be mandatory in metropolitan Melbourne and Mitchell Shire.
"Today, and in line with the advice of the Chief Health Officer, I can announce that same requirement will apply across regional Victoria.
"I understand this will a big step for some. But by covering your face, you're protecting your community, and protecting those extra freedoms your community enjoys.
"By covering your face, you're keeping local businesses open, and keeping local people in work."
Residents in six local government will no longer be able to have visitors to their home.
"From 11:59pm tonight, and in the local government areas of Colac-Otway, Greater Geelong, Surf Coast, Moorabool, Golden Plains, and the Borough of Queenscliffe, you will no longer be able to visit people or have visitors at home," he said.
Watch Daniel Andrews speak below
The huge increase in cases makes it the worst day on record for COVID-19 diagnoses, eclipsing the previous Victorian record of 532 cases recorded on Monday.
Yesterday, 295 new cases of COVID-19 were reported.
As of Wednesday, the rest of Australia combined had seen 84 deaths.
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On Wednesday, Professor Brett Sutton would not say if COVID-19 cases had peaked despite speculation the worst might be behind the state.
"There is nothing else to consider here. We have to watch the numbers every day," he said.
"So I certainly wouldn't say we have definitely passed the peak."