The woman died at the scene after two cars collided at around 7.30am on Monday on the A816 near to Oude Dam, Oban.
The 26-year-old male driver of the other car was taken by ambulance to hospital in Oban. His injuries are not thought to by medical staff to be serious.
Constable Stuart Campbell, of the Oban Policing Unit, said: “Although we have spoken to a number of people who came to assist following the crash, I am keen to hear from the driver of a large dark-coloured 4x4 vehicle in the area just prior to the crash.
“This vehicle was not involved in the crash or anything like that, it’s just we believe they may have seen one of the cars involved and may have information that could assist our investigation.”