Police and paramedics were called to the incident on Poland Street at around 11:40 this morning.
Armed police sealed off neighbouring streets as paramedics worked to save the life of the stabbing victim.
The London Air Ambulance was also called to the scene, situated near the city's world-famous Oxford Street.
The victim, who is believed to have suffered multiple stab injuries, was pronounced dead at the scene at 12:20.
His identity has not yet been released, as police work to inform his family.
A Metropolitan Police spokesperson said a man had been arrested shortly after the stabbing in connection with the incident.
A London Ambulance Service spokesman said: “We were called at 11.36am today to reports of a stabbing in Poland Street, central London.
“We sent an ambulance crew, a paramedic in a fast response car and an incident response officer to the scene.
“We also dispatched London’s Air Ambulance. Our first paramedic arrived in less than seven minutes.
“Despite the best efforts of our teams, the patient sadly died at the scene.”