The accident happened just after 11am last night on Great Western Road, near the Great Western Retail Park, on the boundary between Drumchapel and Clydebank.
Police have confirmed that both men were travelling eastbound in the Suzuki car when it lost control and crashed into a tree between the Drumry Road roundabout and Allerdyce Road.
The men were trapped inside the car and fire crews from Clydebank used cutting equipment to remove the roof and free them.
But sadly the 24-year-old passenger was pronounced dead at the scene.
The driver, aged 25, was rushed to the Western Infirmary to be treated for chest injuries. His condition is today described as "critical".
A section of Great Western Road was closed in both directions for more than five hours last night.
Police say a full report will be sent to the Procurator Fiscal.
Inspector David Carballo of the Road Policing Department based at Helen Street in Glasgow said today: "Extensive enquiries are ongoing to establish the cause of this crash.
"I would urge anyone who witnessed the crash, or who has information that may assist police enquiries to contact Police Scotland on 101."
Station Commander Joe McKay from Clydebank Fire Station said: "Firefighters removed the car's roof to give paramedics access to two men who were trapped inside.
"The crews used their professional skills to quickly and effectively enable the casualties to be released from the car, and they were working closely with ambulance colleagues throughout the operation.
"Sadly, one of the men was confirmed to have died at the scene. The other was taken by ambulance for treatment at the Western Infirmary."
Mr McKay said the collision was the second road rescue operation conducted by firefighters in Clydebank in just days.
On Friday three women were cut free from a car after it crashed on Duntocher Road. One was taken to the Western Infirmary for treatment.