South Yorkshire Police have launched the appeal following the collision between a motorbike and a lorry near Thorne yesterday.
At around 6.30pm, it is reported that a white Transit tipper van was travelling along North Common Road in the direction of Moorends Road, Moorends when a Suzuki GSXS-1000 motorcycle overtook the van.
It is believed that the motorbike then lost control before leaving the road.
Two people, the rider and passenger on the bike, were taken to hospital where they remain.
The passenger, a 44-year-old woman, has suffered life-changing injuries.
The rider, a 48-year-old man, suffered serious injuries.
Officers are now asking anyone who saw what happened to contact them as they continue their enquiries.
Please call 101 quoting incident number 658 of 17 September if you can help.