Former Nickelodeon child star Kianna Underwood has been identified as the victim in a terrible hit-and-run collision that left her dead after she was dragged down two Brooklyn blocks early Friday morning.

Law enforcement sources tell TMZ the 33-year-old -- who appeared on the 2005 series "All That" -- suffered severe trauma to her head and torso ... when a gray vehicle, driven by an unknown suspect, was traveling west on Pitkin Avenue and struck her as she crossed the street at Pitkin and Mother Gaston Blvd.

We’re told Kianna was left lying motionless in the roadway after being dragged under the car for nearly two blocks.

Sources tell TMZ the NYPD received a 911 call around 6:49 AM Friday -- and when EMS arrived, Kianna was pronounced dead at the scene. No arrests have been made at this time.

Kianna was a talented child actress who also starred on Nickelodeon’s "Little Bill."

She was 33.

RIP