The California Highway Patrol says the roughly 16 or 17-year-old boy was spotted on Interstate 580 in Oakland around 6:30 a.m. Friday. He was walking into lanes of traffic when he was struck.
The collision caused several other cars to crash and the freeway's eastbound lanes to close for about an hour.
Three people suffered minor injuries.
It's not clear why the teenager was on the freeway. Authorities say he did not have identification on him.