Victorian Premier Daniel Andrews said the declaration would allow the government to enforce the 14-day isolation period mandated for travellers arriving in Australia.
A state of emergency will come into force in Victoria and the Australian Capital Territory on Monday, as the state response to the coronavirus pandemic ramps up.
The never before used powers under the Health and Wellbeing Act will allow authorities to enforce the 14-day isolation requirements for all travellers coming into Australia, Victorian Premier Daniel Andrews told reporters on Monday.
Prime Minister Scott Morrison first announced the requirement for all people arriving from overseas to self-isolate for two weeks on Sunday, effectively putting Australia's international tourism industry on pause.
In Victoria, the state of emergency will start from midday on Monday and will initially run for four weeks, but is likely to continue after that, Premier Andrews said.
The declaration will allow authorised officers to detain people, restrict movement and prevent entry to premises to protect the public.
Victorian health authorities have now confirmed 71 positive COVID-19 tests after 14 new cases were confirmed overnight.
Shortly after Victoria's announcement, ABC News reported that the ACT's Chief Minister Andrew Barr would announce a state of emergency after the territory confirmed it's second coronavirus case on Sunday.
The death toll from the virus in Australia jumped to five on Sunday evening, after two women, aged 77 and 90, died in Sydney. The number of confirmed infections across the country has also surged to almost 300.
More than 162,000 cases have so far been confirmed across the world. Of these, approximately 75,000 have recovered and more than 6,000 have died.
Coronavirus symptoms can range from mild illness to pneumonia, according to the federal government's website, and can include a fever, coughing, sore throat, fatigue and shortness of breath.
People who believe they may have contracted the virus are advised to call their doctor before visiting or contact the national Coronavirus Health Information Hotline on 1800 020 080.