The diffraction of a beam of electrons by atoms or molecules. Electrons can be diffracted in a similar way to light and X-rays shows that particle can act as waves.

Because of the low penetration, electron diffraction cannot easily be used to investigate crystal structure. It is employed to measure bond lengths and angles of molecules in gases. It is extensively used in the study of solid surfaces and absorption.

The main techniques are low-energy electron diffraction (LEED) in which the electron beam is reflected onto a fluorescent screen, and high-energy electron-diffraction (HEED) used either with reflection or transmission in investigating thin films.