The crash happened just before 1:50 a.m. The CHP says four vehicles were at the scene when they arrived, but more may have been involved.
The rider of a motorcycle was reported down in the middle of the highway. All lanes were stopped and a Sig Alert was issued just after 2 a.m. Officers did CPR on the man, but he died at the scene.
Some lanes were reopened at 3:17 a.m.
The victim is described as a Hayward resident, in his late 30s.
The CHP is looking into who was at fault.