In the whole electromagnetic radiation, the Gamma Radiation has the shortest wavelength.
Order of the waves are as follows (from shortest to longest wavelength):
Gamma, X-Rays, UV, Visible, Infrared, Microwaves, Radio Waves.
Gamma has the shortest wavelength as a result of it's the next frequency, which means a lot of waves in a very second than the other radiation, which ends within the short wavelength.
Wavelength is inversely proportional to the Frequency, and because it has a short wavelength and high frequency it has the most energy out of the rest of the Electromagnetic Radiation