A P-plate driver and his teenage passenger have been seriously injured after their car slammed into a power pole in Sydney's south and split in half.

The pair were travelling in a white Honda sedan along King Georges Road, South Hurstville, about 12.15am today, when the car left the road and slammed into the pole.

The impact split the car in two.

The 20-year-old driver and his 19-year-old passenger were taken to St George Hospital with serious injuries.