Morrison's speech included a ban on non-essential indoor gatherings with more than 100 people and recommendations to avoid all international travel.
What it did not include was the enforcement of an "Australia wide lock down" — even though this message spread through social media networks, instant messaging applications and by text message like wildfire on Tuesday evening.
Different versions of the hoax — which falsely claimed all gatherings, schools, universities, and non-essential government services would be shut down for two weeks — claim to have heard from "a good source in government", "a friend who works in parliament" or an unnamed cabinet leaker.
The information in the post is directly lifted from a March 16 press release from Malaysian prime minister Muhyiddin Yassin about his country's own lockdown — including a reference to the "Muzakarah meeting", which is Malaysia's Muslim council.
The earliest example of the viral hoax found by BuzzFeed News was posted to Reddit — which has struggled to contain misinformation about the coronavirus — to the r/China_Flu subreddit at 5.15pm on March 17. The post was quickly debunked by commenters and deleted (an archived version can still be seen here).
Since then it has spread across Facebook, Reddit and Twitter.
It's made an appearance on popular football web forum, BigFooty.
People have said they've received it by text message.
Even some members of the Australian media shared the hoax.
It is completely untrue. Australia's health minister Greg Hunt tweeted about the viral rumour on Tuesday night, saying "This is false".
What Morrison did announce on Wednesday morning was a number of measures aimed at cracking down on the spread of the coronavirus, including raising Australia's overseas travel advice warning to Level 4 — meaning do not travel — to any country in the world, the first time this has ever happened.
He also announced a ban on nonessential indoor gatherings of more than 100 people, in addition to an earlier ban on outdoor gatherings of 500 or more.
The government's advice from health officials is to not unilaterally shut down schools, universities, public transport or workplaces at this stage.
Morrison said these measures could be in force for six months.