With high levels of community transmission, including 760 current "mystery cases" in Victoria with no known source of infection, drastic steps were necessary, he said on Sunday.
“These are significant steps and not taken lightly. It's very challenging. It's exactly what we have to do,” he continued.
“I'm not prepared to accept that or accept days and days and days of hundreds of cases and more and more death.”
The new restrictions apply to how Victorians live, with further restrictions around work and business to be revealed on Monday. Here is what you need to know.
Melbourne placed under curfew
Metropolitan Melbourne is the first region in Australia to be placed under Stage 4 restrictions.
The most significant of these is a curfew enforced from Sunday, with residents barred from leaving their homes between 8pm and 5am.
During these hours, the only reasons to be outside of your home are to give or receive care, or go to and from work.
Outside the curfew, people will only be allowed to leave the house for four reasons: purchase food and necessary supplies, exercise, give or receive care, or work.
“Going to a mate's place, visiting friends, being out and about for no good reason, all that will do is spread this virus,” Mr Andrews said.
Residents can only travel within five kilometres from their home
Additionally, residents will no longer be able to travel further than five kilometres from their home, unless the reason is to give or receive care.
Only one person per household will be allowed to go shopping once per day, though caregivers and those assisting elderly residents are exempt. People will be able to bring dependent children with them if they are unable to leave them unattended at home.
The five-kilometre limit won’t apply to shared custody arrangements or those visiting intimate partners. The limit also does not apply for those going to work, while those studying must do so at home.
Those escaping family violence are also able to leave their home.
Essential retail outlets, including supermarkets and liquor stores, are still allowed to operate and restaurants and cafes will remain able to offer takeaway and home delivery services, subject to certain conditions.
Recreational activities banned
When it comes to exercise, Melbourne residents will only be able to exercise outside once per day for up to one hour within a five-kilometre radius of their home.
People will able to exercise in groups no bigger than two, though dependent children or other at-risk people in the home who cannot be left unattended are also able to come along.
Recreational activities including tennis, golf and fishing are also banned.
"No golf, tennis, kicking the football or the soccer ball around," Mr Andrews said on Sunday. "It's a run or walk and you have to go straight home."
Further restrictions on wedding and religious services
Funerals remain limited to 10 mourners, with attendees allowed to leave Melbourne to attend ceremonies in regional Victoria.
But from Thursday, weddings will be banned unless an exemption is granted on compassionate grounds.
Religious ceremonies and worship service will be limited to five people.
Regional Victoria to enter Stage Three restrictions
Regional Victoria will revert back to Stage 3 restrictions from midnight on Wednesday, similar to those that have been in place in Melbourne since July.
Residents will only be allowed to leave their homes to shop for essentials, provide care, exercise, work or study.
Time has been given for restaurants and cafes to return to takeaway and home delivery-only services.
Pubs, bars, beauty shops and other venues will also be closed, while community sport will stop.
“We cannot have a situation where this continues to grow and grow in regional Victoria,” Mr Andrews said.
Notably, the Mitchell Shire, which was locked down at the same time as metropolitan Melbourne is now considered part of regional Victoria, and will remain at Stage 3 restrictions.
All Victorian students return to remote learning
All school students across Victoria will return to home learning from Wednesday, though vulnerable students and those whose parents are essential workers will still be permitted to learn on-site.
On Monday students will attend school as normal, with a pupil free day on Tuesday before remote learning begins the following day.
Education Minister James Merlino confirmed Year 12 students will receive their VCE certificate and ATAR score at year’s end.
“We have been really, really conscious of the impact that every decision we have been making in regards to Year 12 students,” he said.
TAFE and university students will also revert to learning from home.
For the first time, childcare and early childhood services will also be closed in Melbourne, with few exemptions.
Childcare centres will remain open across regional Victoria.
Hefty fines for rule-breakers
Any Victorians found to be breaking the new regulations will be served a $1,652 fine.
The cancellation of some overnight public transport services means there will be an increased police presence to enforce the new measures.
Mr Andrews warned Victorians the “time for leniency, the time for warnings and cautions is over".
“If you are not complying, you are going to be pulled up on it. You will be asked and if you don't have the right answer, you can't justify the choices you have made, then you will be fined," the premier said.
“If you are not at home and you should be, if you have the virus and are just going about your business, you will be dealt with harshly.”
Face coverings will also be mandatory for all Victorians, with those who do not wear a mask and who have no lawful excuse to be fined $200.
Metropolitan Melbourne residents are subject to Stage 4 restrictions and must comply with a curfew between the hours of 8pm and 5am. The only reasons for Melbourne residents to leave home during these hours are for exercise, to shop for necessary goods and services, for work, for health care, or to care for a sick or elderly relative.
The full list of restrictions can be found here.
All Victorians must wear a face covering when they leave home, no matter where they live.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.
News and information is available in 63 languages at sbs.com.au/coronavirus