It is understood the girl was riding a bicycle when it was struck by a lorry near the Tesco story in the Upper Newtownards Road area around 9 am.
The girl has been taken to the Royal Victoria Hospital in west Belfast.
The road is currently closed in both directions in the Ballyhackamore area.
Police are at the scene and are advising motorists to expect delays in the area.
The condition of the child is not yet known.