The B3035 between Bishop’s Waltham and Corhampton has been closed while officers deal with with the incident.
A police spokesman said: We were called at 4.31pm to a serious collision between a car and a motorcycle on the B3035 near Corhampton.
‘The B3035 is currently closed between Corhampton Lane near Corhampton and Sailor's Lane towards Bishop's Waltham.’
Witnesses reported seeing an air ambulance, road ambulances and police cars at the scene.
Hampshire Police tweeted: ‘Following a serious collision, the B3035 is currently closed between Corhampton Lane near Corhampton and Sailor's Lane towards Bishop's Waltham.
‘Please avoid the area. We thank you for your patience as we deal with this incident.’