Cosmological and astrophysical observation point to the existence of an exotic type of matter known as Dark Matter (DM) that accounts for about 80% of the mass of the Universe. If DM is realized in the form of weakly interacting massive particles (WIMPs) it could be produced at the LHC pp collider. At colliders, mono-X final states are considered golden channels, for which DM particles are produced in association with energetic jets of hadrons, photons, W/Z bosons or top-quarks. Here we present the latest results from the ATLAS collaboration on the mono-jet and the mono-photon searches in pp collisions at 13 TeV using an integrated luminosity of up to 139 fb-1. The results were translated into exclusion limits in different model for new physics including DM simplifies models, supersymmetry inspired models, models with large extra spatial dimensions, and models for the production of axion-like particles.