A three-year-old boy and his parents have died after their car was hit by a truck at Stoneleigh in western Victoria.

The boy's grandmother was trapped in the wreckage and flown to hospital with life-threatening injuries. She is the sole survivor.

Victoria Police said the family's car failed to stop at a stop sign at about 9:30am and was T-boned at the intersection of Mount William Road and Eurambeen-Streatham Road, about 45 minutes west of Ballarat.

Detective Inspector Craig McEvoy said the car spun several times before landing on its passenger side.

"We believe the car has travelled through the stop sign. The truck had right of way," he said.

"At this point in time, it appears there's no fault of the truck involved.

"There's nothing to indicate excessive speed was a factor."

Police

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