Luxembourg became on Tuesday the third European country to legalise euthanasia after the Netherlands and Belgium, as a new law went into force.
A law published in the official register said that doctors who carry out euthanasia and assisted suicides would not face "penal sanctions" or civil suits for damages and interest.
The law was the source of great controversy in the tiny country where the head of state, deeply catholic Grand Duke Henri, refused to sign off on the bill, triggering a constitutional crisis.
To get around his refusal and avoid such problems in the future, Luxembourg's parliament voted for legislation to give the monarch a purely ceremonial role.
Apart from Luxembourg, the Netherlands and Belgium have been the only EU countries to allow euthanasia since legalising it in 2002 under strict conditions.
In Switzerland, a doctor can provide a patient who wants to die with lethal medication that the patient has to take by him or herself.