The incident occurred on a bus around 10.20 p.m. yesterday (February 28).
Officers and the London Ambulance Service arrived and discovered a critically injured man.
He was taken to the hospital and is still in critical condition.
A crime scene has been established, and parts of Oxford Street remain closed to traffic.
As police investigations continue, no arrests have been made.
Police were called at about 22:20hrs on Tuesday, 28 February to reports of a man stabbed on board a bus on Oxford Street,” a Metropolitan Police spokesperson said.
“Officers arrived and discovered a 25-year-old man critically injured. He was taken to hospital by the London Ambulance Service and is still in critical condition.
A crime scene is in place and parts of Oxford Street remain closed to traffic.
“There are additional officers in the area.
“There have been no arrests and enquiries continue.
“Anyone with information is asked to contact police at 101 and quote reference CAD 7103/28Feb.”
