A police media spokesman said the woman's car hit the bank side of the Glenorchy-Queenstown Rd, about 25km from Queenstown, crossed the centre line and plunged into bush and trees below road level.
She called emergency services at 5.11pm to say she was uninjured but could not get out of her overturned car. Fire Service volunteers helped her from the vehicle.
Police spoke to the driver but the spokesman did not know the cause of the crash or whether charges were likely.