Police launched an investigation after a grey Toyota Auris and a silver Vauxhall Astra collided on the A26 Tonbridge Road at around 3pm. The cars were travelling in opposite directions.
A woman in her 80s, who was a passenger in the Auris, was pronounced dead at the scene.
The driver of the vehicle and a second passenger were taken to hospital in London after suffering serious injuries. The driver was also badly hurt and hospitalised.
Police are appealing for witnesses and dashcam footage of the collision or the vehicles involved.
Anyone with information about the collision is urged to contact the Serious Collision Investigation Unit on 01622 798538 quoting reference DB/DC/77/19 or email email@example.com