Police helicopters Anthony "Aj" Elvalak was seen on Monday drinking water from a table on his family's property in rural New South Wales.
The young boy, who is autistic and does not speak, was last seen at home on Friday.
His family feared that he had been abducted.
But rescuers found AG on a riverbank about 500 meters from his home in the vast property in Putty in the north of the state.
In footage shared by NSW Police, rescuers can be heard saying "I've got the boy."
A three-year-old child missing on a rural property in the Hunter region since Friday has been located following a large-scale search. NSW Police Force
Authorities said AG suffered some scratches on his lower legs and was found soaked in wet clothes but was in good health.
His father, Anthony Elvalak, described it as a "miracle."
More than 100 officers and volunteers spent days searching for his son in the bush. They had earlier passed over the area where he was eventually found.
"The ants bit him and fell but he is alive. He's alive," a jubilant Mr. Elvalak told television crews.
"I know I was acting feverishly, but no one can understand what it was like when we went through what we went through. I feel incredible.
"My leg, my hip, my ankle, I can't walk. I've been in the bush for four days without sleep. We didn't stop."
Local media showed scenes of family members cheering and cheering when they heard the good news.
Prime Minister Scott Morrison also expressed satisfaction, tweeting that he was "glad to hear he is safe."
"I can't imagine how traumatic this experience was for AJ and his parents," he said.
His parents said it was unclear why the boy had wandered.
AJ was playing with his brothers on Friday morning and usually stuck close to his mother.
Police seized a white car on Sunday in the belief that it was investigating a kidnapping case.