Gwent Police are appealing for information after a road traffic collision on the old Abergavenny Road, near Raglan.
It happened at about 11.15am, on Tuesday 29th April, and involved a car and a motorcycle.
Officers attended, alongside personnel from the National Police Air Service, Welsh Ambulance Service, Wales Air Ambulance and South Wales Fire and Rescue.
The motorcyclist, aged 63, was taken to hospital and is in a critical condition.
A spokesman for the police force said:”If you were on Abergavenny Road between 11:00am and 11:30am, and have dash cam footage, please call us on 101, quoting 2500133766. You can also DM us or contact us online: https://orlo.uk/k5LKD
“Alternatively, you can call Crimestoppers anonymously on 0800 555 111 or visit www.crimestoppers-uk.org.”