The  effects  of  extreme  confinement  on  the  electronic,  excitonic, and  radiative  properties  of  atomically  thin  GaN  quantum  wells  were studied through use of first-principles calculations. It was shown that extreme  quantum  confinement  shifts  the  bandgap  of  GaN  into  the deep-ultraviolet (UV) and increases  the exciton binding energy up to 215  meV,  stabilizing  excitons  against  thermal  dissociation  at  room temperature. The luminescence is transverse-electric polarized, which facilitates light extraction from c-plane heterostructures. These results demonstrate  that  atomically  thin  GaN  quantum  wells  exhibit  stable excitons  at  room  temperature  for  potential  applications  in  efficient light  emitters  in  the  deep  UV  as  well  as  room-temperature  excitonic devices.  Deep  UV  light  emission  has  applications  in  germicidal sterilization, water purification, gas sensing, and UV curing.