Extra cash to help prevent people losing their homes has been announced on what has been hailed as a "landmark day" in the fight against homelessness.
From Monday, anyone who loses their home through no fault of their own is entitled to settled accommodation as part of the 2012 homelessness commitment.
Previously, only those classed as being in priority need - often families with children - had that right.
But the Homelessness etc. (Scotland) Act, passed by Holyrood in 2003, abolished the priority need test for homelessness.
The removal of this will give an estimated 3000 more people a year the right to settled accommodation.
As the changes came into force, Ms Sturgeon also announced £300,000 would be spent over the next two years to help councils with their efforts to prevent homelessness.
The Deputy First Minister said: "This is a landmark day in the fight against homelessness.
"I know the heartache and trauma of homelessness from working closely with households faced with the prospect of losing the roof over their head.
"Meeting our 2012 commitment guarantees that those who lose their home from no fault of their own will be guaranteed settled accommodation.
"It is absolutely right to offer this guarantee in a time of crisis for people. It sends the signal that we are there to help, there is hope and that the state will do what it can."
She said Scotland's councils had done "excellent work" ahead of the commitment coming into effect, but added: "Now is not the time to pat ourselves on the back. Instead, we need to redouble our efforts and make sure the commitment works in practice across Scotland.
"That is why we have committed a further £300,000 over the next two years to enable local authorities to continue working together to ensure vital prevention activity continues to result in many more people avoiding entirely the misery of homelessness.
"With homelessness figures already heading in the right direction, today we have taken a huge step forward for Scotland."
Councillor Harry McGuigan, spokesman for the local government body Cosla, said councils had been "pulling out all stops" to meet the 2012 commitment.
He said: "This is a tremendous achievement and it has not always been an easy journey, especially given the recent economic climate and resulting financial pressures.
"Focusing our efforts on helping people avoid crisis and homelessness has been crucial."
Graeme Brown, director of the housing and homelessness charity Shelter Scotland, said: "Scotland can be very proud that it is making history by meeting the 2012 commitment - which is internationally regarded as the cutting edge of progressive homelessness reform.
"I congratulate all the local authorities who have made widespread changes in order to meet their new responsibilities to homeless people."
He added: "This marks a new beginning for Scotland and the way it treats homeless people. The challenge now is to make the 2012 commitment work for all those without a home."