Melissa was last seen on Wednesday.
Gardaí are seeking assistance in locating missing teenager in the midlands.
16-year-old Melissa McDonnell was last seen in the Pearse Street area of Mullingar, County Westmeath, at approximately 6pm on Wednesday 18th October.
Melissa is described as being approximately 5 foot 2 inches in height with a thin build, blonde hair and blue eyes.
When last seen, Melissa was wearing a grey jumper, a green sleeveless jacket and black runners.
Gardaí are concerned for Melissa's welfare.
Anyone with any information on Melissa's whereabouts are asked to contact Mullingar Garda station on 044 938 4000, the Garda Confidential Line on 1800 666 111, or any Garda station.
Gardaí Renew Appeal After Hit And Run In Laois
Fuel Prices Rise As Farmers Leave €65m Support Unclaimed
Barbara Heslin Retires From Longford County Council
Charter Medical Group And Vhi Form Partnership To Ensure Timely Endoscopy Access
Met Éireann Issues High Temperature Warning For 13 Counties
Cyclist In Her 80s Dies Following Bike And Truck Crash
Call For Consent Education To Begin At Pre-School Age
Minister Vows Closer Cooperation On Wildfire And Bogfire Legislation