Katie, who lives in the Chesterfield area, was last seen at about 4.50pm yesterday (Tuesday 17 May) in the Balby area of Doncaster, having left her hometown via public transport.
She is white and described as about 5ft 5in tall, of medium build, with long hair which is darker at the top with lighter highlights at the bottom.
She is still believed to be in the Doncaster area.
In a statement,South Yorkshire Police said: “Officers are becoming increasingly concerned for Katie's welfare and want to speak to anybody who has seen her.
“Have you seen her? Do you know where she might be?”
Anyone with any information which may help police enquiries, call 101 and quote incident number 15 of May 17.
Please visit South Yorkshire Police’s picture gallery here for more information.