Dagmar Johanne Amalie Overbye (23rd April 1887 - 6th May 1929) was a Danish serial killer.
Overbye moved to Copenhagen in 1915, and opened an unofficial adoption business. However, this was in fact a cover for her to murder babies left in her care, either by strangling them, drowning them or burning them alive in her masonry heater. Over the course of seven years, Overbye killed 25 babies, including her own.
After seven years of killing babies, Overbye was caught when a young mother named Karoline Aagesen gave her her illegitimate baby for adoption, then attempted to reclaim it the next day, resulting in Overbye accidently incriminating herself. When the police investigated Overbye, they discovered the remains of Aagesen's baby, and several others. Overbye was convicted of the murders of nine of the babies and sentenced to death, although her sentence was commuted to life imprisonment. Overbye died in jail in 1929.