A motorist hit and severely injured a cyclist in Costa Mesa on Monday, police said.

The 26-year-old driver, whose identity is being withheld, in a 2009 Toyota Corolla hit the 40-year-old cyclist from behind in the 1200 block of Victoria Street about 6 p.m., said Costa Mesa Police Sgt. David Makiyama.

Both the driver and cyclist live in Costa Mesa.

The cyclist suffered major head trauma, Makiyama said. As of Tuesday afternoon, police described his condition as critical.

Witnesses or those with information are asked to contact Traffic Investigator Rick Cummings at (714) 754-5264.

— Bradley Zint

Twitter: @bradleyzint