The accident happened on Great Western Road, Clydebank, West Dunbartonshire, at about 11pm yesterday when the Suzuki lost control, left the road and struck a tree, police said.
Firefighters cut the roof off the car to allow paramedics to treat the two men inside.
The 24-year-old passenger died at the scene and the male driver, 25, was taken to the Western Infirmary in Glasgow for treatment to chest injuries. Hospital staff described his condition as critical.
A report is to be sent to the procurator fiscal.
Inspector David Carballo said: "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."
It is the second serious crash in the area in the last few days.
Firefighters had to use cutting gear to release a woman from a car after a two-car crash in on Duntocher Road on Friday.
Fire commander Joe McKay said: "We have seen two significant road traffic collisions in three days and sadly one man has lost his life.
"It is vital that all motorists recognise the risks and take action to prevent further tragedy.
"Even the most experienced drivers can be caught out by variable conditions at this time of year, with low winter sun and unpredictable weather and surfaces often contributing to collisions.
"If we all accept it can happen to us and follow the Police Scotland advice for safe winter driving, then we can reduce the chances of being involved in a collision."
A motorcyclist has also died after a crashing with a van in Aberdeen.
The collision happened when the 20-year-old male biker struck a Transit van in Balgownie Road at about 6am today.
He was taken to Aberdeen Royal Infirmary but died a short time later, police said. The van driver was uninjured.
The road has been closed while officers investigate the scene and police are appealing for anyone who witnessed the crash to contact them on 101.
Meanwhile, an elderly man who died in hospital after being knocked down has been named by police.
Robert Holmes, 79, was crossing Burnbrae Road in Blantyre, South Lanarkshire, at about 5.40pm on Saturday when he was hit by a grey Honda.
He was taken to Hairmyres Hospital but died later the same evening. The 61-year-old female driver of the Honda was not injured.
Sergeant John Tait said: "We have managed to speak to one person who witnessed the crash, however we would still appeal for anyone else who saw what happened to come forward."