A 29-year-old man and a boy, 17, were in a silver VW Polo when it was involved in the incident on Northam Bridge early on Saturday, Hampshire Constabulary said.
The pair have been arrested on suspicion of causing death by careless or inconsiderate driving and are in custody, the force said.
Emergency crews were called to the incident shortly after 1.20am.
The teenage motorcyclist from Fareham, Hampshire, was on a white Yamaha YZF.
He died in hospital from his injuries.
Hampshire Constabulary has appealed for any witnesses to the collision to come forward.
It said: “We would like to thank motorists for their patience as the Northam Bridge was closed for several hours before it could be reopened.
“We would like to speak to any witnesses and, in particular, anyone with relevant dash cam footage of the incident or the moments leading up to it.”
Anyone with information is asked to contact police.
