The collision happened at the junction of the Castlereagh and Upper Knockbreda roads at around 9.45pm.
Police are appealing for the driver of a red-coloured estate car, who stopped at the scene immediately after the collision to get in touch with them.
Sergeant Marion Curran said: “We are very keen to talk to this person as we believe they may have information that could be vital to our investigation.
“We need their help and would urge them to get in touch with us as soon as possible.
“Anyone who has information that could help police should contact us on the non-emergency number 101, quoting reference 1398 of 27/9/17.”
A man in his 60s was released from hospital following treatment for minor injuries.
A 20 year old man, arrested in connection with the incident, has been released on bail, pending further enquiries.
He is now expected to be re-arrested and questioned about causing the teenager’s death by dangerous driving.