The Orange County Sheriff's Department says Brittany Mitchell walked away from the Orangewood Children's Home Wednesday morning with two other girls.
Those girls returned, but Mitchell did not.
She was last seen at the Block at Orange, and is known to frequent the Anaheim area.
Mitchell is 5 feet tall, 110 pounds with brown hair and brown eyes. She was last seen in all black clothing and a sweatshirt with "CA" on the front.
Anyone with information is urged to call the Orange County Sheriff's Department at (714) 647-7000 or (714) 936-0763. Anonymous tips can also be submitted to Orange County Crime Stoppers at 1-855-TIP-OCCS.