Officers were called by the London Ambulance Service at 8.08pm on Monday to Pield Heath Road near the junction with Copperfield Avenue.
The critically injured man taken to a west London hospital, where his condition is being treated as life-threatening.
No arrests have been made.
Cordons remain at the scene in Uxbridge.
Police are asking witnesses, or anyoner with information, to call them on 101 quoting quoting CAD 7227/14Sep.
To remain anonymous, please contact Crimestoppers.
This is a breaking story. More to follow…