With　the　continuous　development　of　laser　technology　and　the　increasing　demand　for　lasers　of　different　frequencies　in　the　infrared　(IR)　spectrum,　research　on　infrared　nonlinear　optical　(NLO)　crystals　has　garnered　growing　attention.　Currently,　the　three　main　commercially　available　types　of　borate　materials　each　have　their　drawbacks,　which　limit　their　applications　in　various　areas.　Rare-earth　(RE)-based　chalcogenide　compounds,　characterized　by　the　unique　f-electron　configuration,　strong　positive　charges,　and　high　coordination　numbers　of　RE　cations,　often　exhibit　distinctive　optical　responses.　In　the　field　of　IR-NLO　crystals,　they　have　a　research　history　spanning　several　decades,　with　increasing　interest.　However,　there　is　currently　no　comprehensive　review　summarizing　and　analyzing　these　promising　compounds.　In　this　review,　we　categorize　85　representative　examples　out　of　more　than　400　non-centrosymmetric　(NCS)　compounds　into　four　classes　based　on　the　connection　of　different　asymmetric　building　motifs:　(1)　RE-based　chalcogenides　containing　tetrahedral　motifs;　(2)　RE-based　chalcogenides　containing　lone-pair-electron　motifs;　(3)　RE-based　chalcogenides　containing　[BS3]　and　[P2Q6]　motifs;　and　(4)　RE-based　chalcohalides　and　oxychalcogenides.　We　provide　detailed　discussions　on　their　synthesis　methods,　structures,　optical　properties,　and　structure-performance　relationships.　Finally,　we　present　several　favorable　suggestions　to　further　explore　RE-based　chalcogenide　compounds.　These　suggestions　aim　to　approach　these　compounds　from　a　new　perspective　in　the　field　of　structural　chemistry　and　potentially　uncover　hidden　treasures　within　the　extensive　accumulation　of　previous　research.　Non-centrosymmetric　rare-earth-based　chalcogenides　and　their　derivatives　could　offer　novel　insights　into　the　targeted　design　and　exploratory　synthesis　of　new　IR　nonlinear　optical　candidates.