The collision occurred near Fremont and Old Warm Springs boulevards around 5:40 a.m., Fremont police Officer Tiffany Bobbitt said.
The car that struck the bicyclist was described as a four-door, dark-colored 1995 Toyota sedan that was last seen heading south on Fremont Boulevard.
Police said the vehicle may have damage to its front bumper area.
The bicyclist suffered major injuries and was treated at a hospital in San Jose, according to Bobbitt.
Fremont Boulevard was shut down between Old Warm Springs and South Grimmer boulevards as the accident was investigated. The road reopened around 9:45 a.m., Bobbitt said.
Anyone with information is asked to call police at (510) 790-6760.