The accident happened around 6pm on Leeds Road Six Lane Ends.
Police say the boy was knocked down by a Toyota Avensis taxi.
The boy sustained a serious head injury and was taken by air ambulance to Leegs General Infirmary where he is in a critical condition.
All roads at the junction were closed to traffic for some time while the emergency services tended to the injured boy.
Anyone witnesses are asked to contact the police on 101