The emergency services were called to the major road shortly before 7.30am today (June 11).
Police and paramedics attended and the 31-year-old biker was treated for head injuries.
He was taken to hospital where his injuries are believed to be life-threatening.
There have been no arrests but Park Lane remains closed southbound by police over four hours later.
A Met Police spokesperson said: “On Wednesday, 11 June at 07:22hrs, police were called by the London Ambulance Service to a road traffic collision between a van and a motorcycle in Park Lane, Westminster.
“Officers attended alongside paramedics who treated the motorcycle rider, a 31-year-old man, at the scene before transporting him to hospital where he remains.
“His injuries are believed to be life-threatening.
“No arrests have been made at this stage. The road remains closed.”
A London Ambulance Service spokesperson said: ““We were called at 7.19am today (11 June) to reports of a road traffic collision at the junction of Park Lane and Upper Brook Street.
“We sent a number of resources to the scene, including an ambulance crew, an advanced paramedic, an incident response officer and a clinical team manager.
“We also dispatched a trauma team in a car from London’s Air Ambulance.
“We treated a man for a head injury and took him to a major trauma centre by road as a priority.”
