Organic-inorganic　hybrid　manganese(II)　halides　(OIMnHs)　have　garnered　tremendous　interest　across　a　wide　array　of　research　fields　owing　to　their　outstanding　optical　properties,　abundant　structural　diversity,　low-cost　solution　processibility,　and　low　toxicity,　which　make　them　extremely　suitable　for　use　as　a　new　class　of　luminescent　materials　for　various　optoelectronic　applications.　Over　the　past　years,　a　plethora　of　OIMnHs　with　different　structural　dimensionalities　and　multifunctionalities　such　as　efficient　photoluminescence　(PL),　radioluminescence,　circularly　polarized　luminescence,　and　mechanoluminescence　have　been　newly　created　by　judicious　screening　of　the　organic　cations　and　inorganic　Mn(II)　polyhedra.　Specifically,　through　precise　molecular　and　structural　engineering,　a　series　of　OIMnHs　with　near-unity　PL　quantum　yields,　high　anti-thermal　quenching　properties,　and　excellent　stability　in　harsh　conditions　have　been　devised　and　explored　for　applications　in　light-emitting　diodes　(LEDs),　X-ray　scintillators,　multimodal　anti-counterfeiting,　and　fluorescent　sensing.　In　this　review,　the　latest　advancements　in　the　development　of　OIMnHs　as　efficient　light-emitting　materials　are　summarized,　which　covers　from　their　fundamental　physicochemical　properties　to　advanced　optoelectronic　applications,　with　an　emphasis　on　the　structural　and　functionality　design　especially　for　LEDs　and　X-ray　detection　and　imaging.　Current　challenges　and　future　efforts　to　unlock　the　potentials　of　these　promising　materials　are　also　envisioned.　This　review　focuses　on　the　latest　advancements　in　the　development　of　organic-inorganic　hybrid　manganese(II)　halides　as　efficient　light-emitting　materials,　which　covers　from　their　fundamental　physicochemical　properties　to　advanced　optoelectronic　applications,　with　an　emphasis　on　the　structural　and　functionality　design　especially　for　light-emitting　diodes　and　X-ray　scintillators.　Current　challenges　and　future　efforts　toward　this　active　research　field　are　envisioned.　image