Marcela Tokarova, 17, was reported missing from Dumfries shortly before 10 pm on Tuesday.
She is five foot in height, has long blonde hair and was last seen wearing a green jacket, orange t-shirt, black jogging bottoms and green Nike air max trainers.
Marcela is known to travel by train or by trying to get a lift.
A police spokesman said: “We believe she may currently be in the Ayrshire area.
“There are growing concerns for Marcela’s safety and her wellbeing and we urge anyone with any information that may assist us in tracing Marcela to phone 101 as soon as possible quoting ref 3946 of July 7.”