The MONNET facility at JRC-Geel is a high-intensity quasi mono-energetic neutron source driven by a 3.5 MV tandem electrostatic accelerator that produces continuous or pulsed ion beams. It complements the GELINA neutron time-of-flight facility by enabling measurements in the MeV energy range (up to 24 MeV), where resonance structures are averaged out and conditions are better suited for weak cross sections and small sample quantities. The accelerator produces proton, deuteron, and helium ion beams with currents up to 100 µA in DC mode and up to 10 µA in pulsed mode, with pulse repetition rates of 2.5, 1.25, or 0.625 MHz and pulse lengths below 2 ns (FWHM). Voltage stability is better than ±0.01%. Neutron energies are defined by the accelerated particle type and energy, the target material (lithium, deuterium, or tritium), and the emission angle. The resulting neutron fluence covers peak energies from 0.3–10 MeV and 16–24 MeV at 0°. The facility has one beam line used for activation, fission, and scattering experiments, operating continuously 24/7 in weekly runs, with only one experimental setup active at a time.