Gardaí in Arklow, Co Wicklow, are looking for 17-year-old Lauren Brennan also known as Lauren Larrissey.
Lauren was last seen on August 17, near Chancery Street in Dublin 7 at around 1pm.
Lauren is 5ft 7in tall with fair hair and blue eyes.
When last seen, Lauren was wearing blue jeans, a mustard coloured top, with a kaki green jacket.
Gardaí are asking anyone who may have seen Lauren to contact them at Arklow garda station on 0402-26320 or the Garda Confidential Line 1800 666 111.