The woman died at the scene in Preston New Road after a Mercedes car hit her and her 65-year-old male companion whilst the pair were out walking at 6.50am.
The Mercedes had been travelling east, in the direction of Blackburn, when the incident happened.
Police said the woman suffered 'significant' head and chest injuries and was pronounced dead at the scene.
Her 65-year-old male companion was also seriously injured and remains at Royal Preston Hospital where he is receiving treatment for a broken leg and a broken jaw.
The driver of the Mercedes c220 was not injured in the collision.
Police confirmed that the driver stopped immediately after the collision and called 999.
He has not been arrested, but police are appealing to anyone who witnessed the incident to come forward to help their investigation.
"A woman has died and our thoughts are with her family at this incredibly difficult time.
"Specially trained officers have been appointed to support them. Our thoughts also remain with the man who is seriously injured in hospital.
"We are appealing to anyone who witnessed the collision and has not yet spoken to us to come forward.
"Likewise, if you have any dash cam footage that could be helpful to the investigation, we would like to hear from you."
Preston New Road was closed for 5 hours - from 7am until midday - from junction 31 of the M6, whilst specialist collision investigators attended the scene.
The busy A-road was also closed at the roundabout junction with the A59, opposite the Mercure Preston Samlesbury Hotel.
Anyone with information is urged to call 101 quoting log number 338 of September 8.