The collision took place at around 10.30pm, when a black Vauxhall Vectra, driving along Bawtry Road towards Doncaster town centre, collided with two pedestrians.
A South Yorkshire Police spokesman said: "One of the pedestrians, a 30-year-old woman, suffered minor injuries in the collision. The second pedestrian, a 27-year-old woman, suffered serious injuries. They were both taken to hospital for treatment.
"Enquires are currently ongoing and officers are appealing for any witnesses who may have seen the collision, or where in the area at the time, to please contact police.
Anyone with information is asked to call South Yorkshire Police on 101, quoting incident number 1144 of June 30.