The boy had been heading towards a Sainsbury’s supermarket around 10pm on Tuesday when he was struck by a “white saloon-style vehicle”.
The incident happened as he crossed Uxbridge Road, at the roundabout with Wellington Street.
The driver failed to stop, instead driving away along Uxbridge Road.
The victim suffered serious injuries and was taken to Wexham Park Hospital, where he is said to be in a stable condition.
No arrests had been made as of Wednesday afternoon, as Thames Valley Police issued an appeal for witnesses.
Investigating officer PC Nadeem Salaam, of the Joint Operations Roads Policing Unit, said: “I am appealing for any witnesses to this collision, whereby a young man has sustained serious injuries, to please come forward.
“Also, if you were driving in the area around the time of the collision and have dash-cam, I’d also ask that you check any recordings in case it has captured something that could assist our investigation.
“You can upload any footage to our dedicated online portal.
“You can contact us by calling the 24-hour non-emergency number 101 or by making a report on our website, quoting reference number 43220578988.”