GENE (Gyrokinetic Electromagnetic Numerical Experiment) is an open source plasma microturbulence code which can be used to efficiently compute gyroradius-scale fluctuations and the resulting transport coefficients in magnetized fusion/astrophysical plasmas. GENE is physically comprehensive, well benchmarked, portable, and highly scalable. GENE is freely available via this webpage, and it is further developed by an international collaboration of physicists and computational scientists which is always open for new contributers. GENE has been used, among other things, to address both fundamental issues in plasma turbulence research and to perform comparisons with tokamak and stellarator experiments. GENE is coupled to the geometry interface code GIST.