Emergency services were called at around 10pm on Thursday (December 7) to reports of two women injured following a collision with a car in Marylebone Road, at the junction with Allsops Place.
The Metropolitan Police, London Ambulance Service and the London Air Ambulance all attended the scene.
One of the women, believed aged in her 50s, received treatment but despite the efforts of the emergency services, she was pronounced dead at the scene, Scotland Yard said.
The second woman, believed aged in her 40s, was taken to hospital but has since been discharged.
Road closures remain in place at the scene.
The car failed to stop at the scene and was found parked nearby.
Two men – aged 29 and 38 – subsequently attended a police station and have been arrested on suspicion of causing death by dangerous driving and failing to stop.
Both remain in custody.
Anyone who witnessed or who has footage of this incident, or any road users with dashcam footage, should call 101 or ‘X’ @MetCC and quote CAD7169/7Dec.
You can also provide information anonymously to the independent charity Crimestoppers on 0800 555 111.