The child had to be taken to hospital by air ambulance, where he remains with life-threatening injuries.
At about 1.50pm, there was a collision between a white Scania HGV lorry and a red Mini Cooper, both travelling northbound on the A1, just after junction 36 for Warmsworth.
The child was travelling in the Mini at the time of the smash.
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South Yorkshire Police are appealing to anyone who may have witnessed the crash today to come forward.
Officers are investigating and would ask anyone who was travelling on the A1, either south or northbound, at around the same time and who may have witnessed the collision, or either vehicle prior to the incident taking place, to please come forward.
The southbound carriageway of the A1 was closed for a short period of time to allow for the Air Ambulance to land.
The 56-year-old man driving the HGV and the 42-year-old woman driving the Mini are not believed to have suffered any injuries.
If you can help, please call 101 quoting incident number 580 of 16 August 2016.