The woman crashed into a tree at the intersection of Culver Drive and Bryan Avenue on Sunday at about 12:45 a.m., according to Irvine police.
Video from the incident shows the woman's SUV fully engulfed in flames.
The good Samaritan said the driver ran a light, narrowly missed him before she crashed.
"When I reached up to her truck, she was unconscious, so me and another bystander pulled her out from that vehicle," the witness said.
The 26-year-old woman from Orange suffered only minor injuries and was arrested on suspicion of DUI.