A girl, 18, was taken to Ysbyty Gwynedd, Bangor after the crash, which happened on the A4086 at about 07:00 BST on Thursday.
Four others were also taken to hospital, but their injuries are not believed to be life-threatening or life-changing.
The boy's family is being supported by specialist officers, and police have appealed for witnesses.
A 17-year-old boy has died after a road crash near Capel Curig.