San Antonio police say Christian Ortiz crashed into the back of an 18-wheeler stopped at a red light on the city's north side just after midnight Wednesday.
Ortiz's Hyundai was trapped in his vehicle that was wedged underneath the big rig.
The 27-year-old was airlifted to University Hospital.
The truck driver was uninjured.
Authorities believe inattention and faulty evasive action were contributing factors to the accident.