Stringent new measures to fight coronavirus will see a ban on people gathering in public and restrictions on people leaving their homes.
Nicola Sturgeon said it amounted to a "lockdown" but was necessary to slow the spread of Covid-19, ease pressure on the NHS and save lives.
In a public address at St Andrew's House in Edinburgh, she said people should stay at home.
It came on the day the death toll from the virus rose to 335 in the UK.
The first minister was speaking after Boris Johnson announced draconian measures for at least three weeks which will see the closure of non-essential shops, libraries, playgrounds and outdoor gyms, and places of worship.
From now on, people must stay at home except for:
- Essential shopping - for food or medicines and only once a day
- Exercise - only once a day and alone, or with someone from your household
- Medical reasons or for the care of vulnerable people
- Travel to and from essential work - all employers should be making provision to work from home
Retailers selling non-essential goods were told to shut and gatherings in public of more than two people who do not live together are to be prohibited.
The first minister said: "Let me blunt. The stringent restrictions on our normal day to day lives that I'm about to set out are difficult and they are unprecedented. They amount effectively to what has been described as a lockdown."
"I am not going to sugarcoat it in any way," the first minister said. "Coronavirus is the biggest challenge of our lifetime.
"Stay at home," she said. "That is the message I gave yesterday and I am reinforcing that message now."
The first minister said a list would be published detailing what was being imposed.
She said that there should, from Monday night, be no celebratory events involving groups of people, therefore no weddings, no christenings.
She expressed her sadness at having to impose a restriction on funerals to immediate family only.
She said: "I know how hard this is, but it is essential'.
To support the new measures and ensure compliance she revealed:
- all non-essential shops will be required to close
- libraries, communal places within parks and places of worship must close
- social events must not take place - including weddings and christenings.
- funerals are restricted to immediate family only
- gatherings of more than two people will be prohibited, unless part of a household or related to essential work.
Nicola Sturgeon said the public should not see these measures as advice, but "a set of rules" to be followed for the protection of ourselves, the community and the NHS.
She said the majority of people would "do the right thing" but that within days emergency legislation would provide powers of enforcement which "would be used if necessary".
Ahead of the new powers being introduced, police will give "strong advice" to those in breach of the measures to "cease and do the right thing".
This will be followed by enforcement powers later this week, which will "likely take the form of fines".
She concluded: "If we do all of these things, if all of us do all of these things, if we all agree, however difficult, to restrict our own lives for a period then many fewer of us will die of this virus than would otherwise be the case.
"Let's all do what we are being asked to do now to protect our own health and that of others and to show love and solidarity for our fellow citizens."
The number of coronavirus deaths in Scotland has increased by four to 14, with 499 people testing positive for Covid-19.
Ms Sturgeon said earlier that these figures were likely to be underestimates - but still showed "the scale of the challenge".
The chief medical officer for Scotland, Dr Catherine Calderwood, said: "Those 14 deaths probably each represent up to 1,000 people that have become infected.
"We have 23 people currently in our intensive care units across Scotland who have coronavirus and each of them represents perhaps 400 to 500 other people that will have become infected in the course of their illness."