The accident happened around 3 a.m. The deputy was on duty at the time, heading southbound on Marguerite Parkway. He somehow lost control of his cruiser, slammed into a light pole and was ejected from the vehicle.
The deputy was transported to Mission Hospital. According to the sheriff's department, the deputy suffered a head injury and is in critical condition.
The deputy is a 13-year veteran of the force, currently part of the Mission Viejo division.
"I ask each of you to keep him, along with his family, in your prayers. This is all very difficult for all of us," said Orange County Sheriff's Capt. Jim Rudy.
Marguerite Parkway was closed in both directions from Vista Del Lago to Alarcon for a Major Accident Reconstruction Team investigation.
The cause of the accident was not immediately clear, though slick roads and foggy conditions may have been a factor. Investigators have determined the deputy was not in pursuit of anyone at the time of the crash.
Investigators are also still determining how fast the deputy was traveling. The light pole was so damaged by the impact that it cracked in half and snapped off at its base.
The sheriff's department wouldn't say if the deputy was wearing a seatbelt.