Organ donation: Presumed consent to start in December 2015
People in Wales will be presumed to have agreed for their organs to be donated after death from December 2015.
Wales will be the first UK nation to introduce a system where consent is assumed unless people have opted out.
The legislation, described by ministers as the "most significant" the Welsh assembly had passed, received royal assent on Tuesday.
Currently, people across the UK join a voluntary scheme and carry a card if they wish to donate organs.
A two-year information campaign is planned in Wales, to ensure everyone is aware of the changes.
'Many die waiting'
First Minister Carwyn Jones said: "The Human Transplantation (Wales) Act 2013 is arguably the most significant piece of legislation passed by the National Assembly for Wales since it acquired full lawmaking powers in 2011.
"Many people will wait years for a transplant but sadly, many die waiting on the list.
"The shortage of human organs continues to cause otherwise preventable deaths and suffering.
"This law will not only help reduce the waiting list, but will also help save lives by reducing the number of people who needlessly die waiting for an organ transplant."
The Welsh government hopes to raise transplant rates by 25%.
As happens now, organs could go to recipients anywhere in the UK, not just in Wales.
Health Minister Mark Drakeford said there would be a public information campaign before the new system comes into force on 1 December, 2015.
"During this two year campaign, people will be given plenty of information on how the new system works and what their choices are," he said.
"Even today, though, people can help others by ensuring their loved ones know their wishes about organ donation and I would encourage everyone to have that conversation."
According to the NHS Blood and Transplant service, there are about 250 people on a waiting list for a transplant at any one time, and 33 people in Wales died in 2012/13 while on the list.
Kidney Wales Foundation chief executive Roy Thomas said it had been a "long journey" to create a "very good law".
"It received proper consultation and first class scrutiny all the way through," he said.
"It gives hope to all those waiting for a transplant, not only those on the list but those who fear chronic organ failure and who may need a transplant."
Evidence from other countries with an opt-out system indicates that the rise in organ donors is small with about 15 additional donors provided each year and approximately 45 extra organs.
There has been opposition to the scheme but ministers have insisted it will be implemented sensitively.