Hampshire police said the 35-year-old man was in collision with a blue VW Polo at 11.30pm on the northbound carriageway of the A3, close to junction 1.
He suffered serious injuries and was pronounced dead at the scene.
The driver of the car was uninjured and is helping police with enquiries.
A police spokeswoman said: ‘Officers from the Road Policing Unit are investigating the exact circumstances of this incident and would like to hear from any witnesses who saw what happened.
‘The driver of the VW Polo was uninjured and is helping officers with their enquiries.
‘Anyone with information about this incident is asked to call Acting Police Sergeant Melanie Adcock on 101, quoting Operation Windy, or Crimestoppers anonymously on 0800 555 111.’
Hampshire police originally said this crash happened on the A3 but have now clarified it happened on the A3M.