Emergency services were called about 1.55pm following reports a child had been hit by a falling tree in Tiwi, a suburb in northern Darwin, while playing in the backyard.
The girl was rushed to Royal Darwin Hospital, but died before arrival.
An 11-year-old boy was also struck by the tree and suffered non-life threatening injuries.
The incident is not believed to be suspicious.
An investigation into the girl’s death is ongoing and a report will be prepared for the coroner.