Investigators say a speeding Ford Taurus collided with a pickup truck before crashing into other cars and a motorcycle.
The driver of the Taurus was identified as Julia Allen, 27, of Newport Beach.
Christopher De La Cruz, 49, of Laguna Niguel and Linda Burnett, 69, of Santa Ana were in the pickup and also died.
Three others were injured, one critically, but expected to survive.
The crash sent Allen's car into the air and into either other vehicles.
Allen was a standout distance runner who went to Stanford University.
"Super athlete," said Bill Sumner, a friend of Allen. "Probably a better kid than an athlete. Everybody loved her. She didn't have an enemy in the world."