Searches for dark matter and extra dimensions with the ATLAS detector

Different approaches to finding evidence for dark matter at the LHC are presented. These include searches for events with large missing transverse momentum and a single jet, photon or W/Z boson. Searches for hidden sectors in events with long-lived particles resulting in displaced hadronic vertices or lepton-jet signatures are also reported. Finally, studies sensitive to the presence of extra spatial dimensions are described, as for example classical and quantum black holes and other non-resonant phenomena. Results from $\sqrt{s}=8$ TeV data taking are presented.