The unnamed 17-year-old is the first minor to be allowed to die under new ruled adopted in 2014, allowing voluntary euthanasia for people of all ages.
Wim Distelmans, who chairs Belgium’s Federal Control and Evaluation Committee on Euthanasia, said in an emailed statement that the first case was reported to his committee by a local doctor last week.
The underage person was reported as being critically ill but no other information was given.
Belgium legalised euthanasia in 2002, and two years ago amended the rules to permit doctor-assisted death for minors in a hopeless medical situation.
It is the only country in the world allowing euthanasia on minors of all ages. In the neighbouring Netherlands the practice is possible for children aged at least 12.
Between 2003 and 2013, the number of patients being euthanised in Belgium rose nearly eight-fold to a total number of 8,752 cases, according to records of the national euthanasia control committee.
In the UK, euthanasia is illegal under English law and is regarded as either manslaughter or murder, with a maximum penalty of up to life imprisonment.