Police have launched a homicide investigation in the Auckland suburb of Manukau.
They said a man arrived at the Manukau Police Station about 1am on Monday and the body was discovered shortly afterwards.
The 37-year-old was known to the child and their family, police say.
He was due to appear in Manukau District Court today charged with murder.
A post-mortem and other inquiries would be carried out this week.
Victim Support is providing the child's mother and family with assistance and support.