The silver Mitsubishi Shogun came off the A920 Colpy to Oldmeldrum road near Tocher in Aberdeenshire yesterday afternoon.
The two female back-seat passengers were pronounced dead at the scene, police said.
The male driver and the woman who was in the front passenger seat suffered "multiple serious injuries". They were taken by ambulance to Aberdeen Royal Infirmary, where they are both said to be in a critical condition.
Police, fire and ambulance crews all attended the scene of the single-vehicle crash, which happened at around 4.10pm.
Sergeant Chris Whelan, from Police Scotland's road policing department, said: "This is a very tragic incident involving the deaths of two elderly ladies.
"It appears that the vehicle was travelling eastwards on the road heading towards Oldmeldrum when it appears to have left the road and struck a tree.
"We are currently trying to establish why this has happened and the cause for the loss of control.
"I wish to appeal to any motorists who were travelling on the A920 about 4pm and had seen the silver Mitsubishi Shogun 4x4 vehicle.
"I would be particularly keen to hear from anyone who may be able to describe the manner in which this vehicle was being driven prior to the collision."
Police can be contacted by dialling the non-emergency 101 number.