The crash happened at the intersection of West Rockland Road and the Des Plaines River walking trail.
A 33-year-old man from Mundelein was riding his bike north on the Des Plaines River Trail when he attempted to cross West Rockland Road.
He was then struck by a westbound Toyota Prius, driven by a 39-year-old man from Gurnee.
The sheriff said the bicyclist was thrown onto the vehicle's front windshield before he fell to the ground.
The bicyclist was transported to a nearby hospital with critical, life-threatening injuries.
The driver of the Toyota, as well as a child passenger, were uninjured.
The Lake County Sheriff's Office Technical Crash Investigations Team continues to investigate the incident.
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Family members started a GoFundMe to raise money for the victim.