Neighbours called triple zero after seeing a young child unresponsive in the front yard of the southern Queensland home about 4.45pm on Monday, police said.
When emergency services arrived at the Moore Park Beach residence, north of Bundaberg, they found a three-year-old girl with a number of wounds.
She died at the scene.
The child's 32-year-old mother was taken into custody and later charged with murder.
A crime scene was established at the property, where police seized a knife.
Acting Superintendent Brad Inskip said two other children, aged one and two, were also at the property at the time, but neither was injured.
Both are in the care of another family member.
Supt Inskip said mental health and any prior interactions with police would likely form part of the investigation into the incident.
Community members have been urged to seek support after the incident, with Supt Inskip saying first responders had encountered an "horrific" scene.
"It's a terrible, terrible incident for everybody, including the witnesses and neighbours, the emergency services, police and ambulance who attended and the investigators who are doing the ongoing investigation," he told reporters in Bundaberg.
"This is not something that we ever want to attend."
The woman was set to face Bundaberg Magistrates Court on Tuesday.
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