Just before 9.15 p.m., police were called to Castlemeads Way in response to a report of a collision involving a black pedal cycle and a dark blue Volkswagen Golf.
The 18-year-old cyclist was pronounced dead at the site despite the best efforts of the public and emergency personnel. His family has been notified.
A 23-year-old Newent resident was detained by police after being accused of killing someone by reckless driving.
Any witnesses to the collision who have not yet spoken to police or who have dashcam footage of the incident are welcome to contact the investigating officers.
While emergency personnel were still on the site, a traffic closure was implemented; it has now been lifted.