A 13-year-old girl from the town of Lavrio, southeast of Athens, has given birth at a clinic in the Greek capital.
In an announcement on Thursday the clinic said that both mother and infant are in good health and are recovering.
The young mother was rushed to a Lavrio health centre on Tuesday with labor pains. After she received first aid she was transferred to an Athens clinic where she gave birth.
The sex of the infant was not immediately known.
The case is very rare and it contradicts the trend according to which Greek women become mothers at an older age than the EU average.
According to the statistics released by Eurostat, Greece ranks lower than the EU average for the percentage of women that become mothers before age 20 (3.7 percent against 5 percent for the EU average).
World Bank data show Greece has seen a significant fall in its adolescent fertility rate, defined as births per 1,000 females aged 15-19.
In 1960 there were 17 births per 1,000 females in this age bracket but this fell to just seven in 2015.
Overall, Greece has seen a significant fall in its birth rate due to the economic crisis. Abortion rates have also risen.