The young driver was attempting to cross the vast country solo when he was stopped by police in Broken Hill, New South Wales, on Saturday.
The highway patrol approached him because there was some light damage to the rear of the vehicle, a police statement said.
When checks revealed the driver was only 12 years old, he was taken to Broken Hill police station.
The boy's ambitious journey began in Kendall, News South Wales, and he was headed to Perth in Western Australia when he was stopped, police said.
The drive to Perth would have covered an enormous 4,000 kilometers (2,485 miles) in total -- the equivalent of driving from New York to Las Vegas, or three times the length of the UK. If he'd driven non-stop, it would have taken more than 40 hours.
It was not immediately clear why the boy embarked on his trip. Social media users expressed some surprise that he had managed to get as far as he did.