Police are appealing for witnesses to a collision which happened on the A120 between Bradwell and Coggeshall this morning, Friday, March 18.
A W registration red Vauxhall Corsa was involved in a collision with a red Ford Fiesta at around 8.20am.
The woman driver of the Corsa, aged in her 40s from Colchester, suffered serious injuries and was taken by ambulance to Addenbrookes Hospital in Cambridge where her condition is described as critical.
The driver of the other vehicle was uninjured.
Officers are particularly keen to hear from anyone who saw the Corsa, which was travelling towards Braintree, before the collision.
Anyone with information is asked to contact Pc Martyn Wells at the Serious Collision Investigation Unit on 101 or email email@example.com