Photoelectronic　performance　of　organic-inorganic　hybrid　perovskites　has　been　investigated　extensively.　Advancement　in　optoelectronic　characterization　and　application　of　this　group　of　materials　in　solar　cells,　light-emitting　diodes,　and　lasers　has　been　pushed　forward　rapidly.　However,　nonlinear　optical　properties　for　applications　in　optical　logic　devices　have　not　been　exploited.　Moreover,　long-lived　excitons　and　charges　limit　the　response　speed　of　such　materials　and　further　construction　of　ultrafast　devices.　In　this　work,　we　make　use　of　the　high　third-order　optical　nonlinearity　of　(CH3NH3)PbBr3　single　crystals　and　develop　a　femtosecond　optical　switch　(OS)　based　on　strong　two-photon　processes　through　absorbing　one　pump　and　one　probe　photon.　The　fascinating　band　structure,　with　a　steep　edge　at　2.22　eV　between　the　transmission　and　strong　absorption　bands,　endows　single　crystals　of　(CH3NH3)PbBr3　with　perfect　characteristics　for　two-photon　optical　switching　in　the　near　infrared.　An　on-off　ratio　of　the　probe　pulses　of　about　90%　and　a　speed　faster　than　400　fs　have　been　achieved　for　this　OS　device.　To　the　best　of　our　knowledge,　such　high　efficiency　has　not　been　realized　for　an　ultrafast　OS　with　any　other　materials　and　devices.　Moreover,　this　is　a　first　exploration,　to　our　best　knowledge,　of　the　third-order　optical　nonlinearity　of　organic-inorganic　hybrid　halide　perovskites　for　application　in　ultrafast　optical　logic　devices　with　high　reliability　and　low　threshold　in　the　near　infrared.　(C)　2021　Optical　Society　of　America　under　the　terms　of　the　OSA　Open　Access　Publishing　Agreement