The incident happened at 17th Street and Cabrillo Park Drive at about 6:45 p.m. Police say the boy was crossing the street with his brother when he was struck by a 2008 Ford F-150 and thrown about 40 feet.
According to Cmdr. Enrique Esparza of the Santa Ana Police Department, the truck failed to stop at the light when it hit the child.
The child was rushed to the hospital with life threatening injuries. He remains in critical condition.
The female driver, identified as 33-year-old Suray Leon of Santa Ana, remained at the scene. She was arrested for felony DUI.
City News Service contributed to this report.