The ban applies to anyone who has been in South Africa, Namibia, Zimbabwe, Botswana, Lesotho, Eswatini, the Seychelles, Malawi and Mozambique.
Health Minister Greg Hunt said the ban was because of the emergence of the Omicron variant — originally identified as b.1.1.529 — in those countries.
Australian citizens, residents and their dependents from those countries will need to go into immediate supervised quarantine for 14 days.
International students and skilled migrants who have also been in those countries will also need to quarantine.
Anyone who has been in those countries in the past 14 days will be required to immediately quarantine.
All flights from those nations will be immediately suspended for 14 days.
“There are currently no known cases of the Omicron variant in Australia,” Mr Hunt said.
“And we’d just note that there are 20 people in quarantine in Howard Springs in the Northern Territory who’ve arrived from South Africa in the last week.”
One person in Howard Springs from South Africa has tested positive, but it is not known if they have the Omicron variant.
Everyone arriving in Australia from overseas will now need to show their 14-day travel history to ensure they haven’t been in southern Africa.
Chief Medical Officer Paul Kelly said there is not yet any clear indication Omicron is more severe than other variants.
“We do know that it does contain a large number of mutations,” Dr Kelly said.
“It is quite different to previous variants that we have been watching.”
Mr Hunt was asked by a reporter if the measure was strong enough given there were already reported cases in Belgium and the Netherlands.
“These are strong, swift, decisive, and immediate actions,” Mr Hunt said.
“We can move at any time to strengthen or to reduce these requirements based on the medical evidence.
“If more actions are required, we will not hesitate.”
Speaking earlier today, NSW Health Minister Brad Hazzard said it’s “likely” Omicron is more transmissible than Delta and has asked anyone who has entered the state from South Africa to monitor for symptoms.
“Anyone who has come in to NSW has been in South Africa in the last 14 days, we ask you to be very, very aware of your symptoms,” he said.
“Contact NSW Health and to self isolate until further instruction.
“It’s crucial to keep our community as safe as possible.”