Emergency services were called after four cars crashed near Pyecombe services at about 4am today (January 11).
A police appeal stated the woman, of Newhaven, who was driving a blue Renault driver, was declared dead at the scene.
No one else was seriously injured in the crash, which involved a blue Volkswagen, black BMW, black Mitsubishi and blue Renault.
Four fire and 11 South East Coast Ambulance Service crews including the air ambulance road vehicle were called.
A spokesman for West Sussex Fire and Rescue Service said firefighters freed a woman after a car overturned and went into a ditch.
The northbound carriage was closed whilst recovery work took place and a diversion was set up via the A281. The A23 fully reopened at around 10.30am.
Sergeant Peter Verney said: “We would like to hear from anyone who may have seen what happened just prior to the collision.
“Witnesses can email [email protected] or call 101 quoting Operation Entwine.”
Traffic was very slow on the A281 between the Henfield Turn Off (A23) and Poynings Crossway.
Crews from the Brighton area and Worthing’s specialist road accident fire engine were in attendance for more than two hours.
Motorists were also delayed northbound on the A24 Findon because of flooding. Congestion was reported at its junctions with the A27 in Worthing and A283 in Washington.
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