Beatrice Coughlan from Eden Gate was last seen in the Delgany area on Thursday.
She's 5' foot 3" in height, of slim build with long fair hair which was in a ponytail.
She was wearing dark trousers, black Nike runners, a beige three-quarter length coat and a beige jumper.
Gardaí and Beatrice's family are concerned for her well-being.
Anyone with information is asked to contact Greystones Garda Station.