The 42-year-old man was riding near Anneport Quarry on La Route d’Anneport in St Martin at around 11.30 am yesterday.
According to a statement from the police, he had been riding from the direction of Gorey village on a red BMW 1000 motorcycle.
He lost control of the bike on the corner by the quarry and was then hit by a blue-coloured Volkswagen that had been driving in the other direction.
The rider was treated at the scene before being treated at the hospital, but he was flown out to Southampton late last night.
The police are appealing for any witnesses – or anyone with any information – to get in touch with them on 612612.
The road was closed for most of yesterday while specialist forensic crash investigators examined the scene.