Birefringent　crystals　are　essential　components　in　modern　optical　devices.　Exploring　new　material　systems　capable　of　serving　as　birefringent　materials　is　of　great　significance　for　the　advancement　of　optical　technology.　In　this　study,　we　propose　a　method　to　enhance　the　birefringence　of　compounds　through　the　assembly　of　multiple　functional　groups.　For　the　first　time,　we　combined　Hg2+,　(SeO3)2−,　and　(TeO3)2−　groups　to　successfully　synthesize　a　new　compound,　Hg2(SeO3)(TeO3).　This　compound　exhibits　a　birefringence　of　0.097@546　nm,　along　with　excellent　thermal　stability　up　to　420　°C　and　a　broad　transmission　window　from　0.32　to　6.3　μm.　Notably,　Hg2(SeO3)(TeO3)　is　the　first　Hg-based　tellurite-selenite　birefringent　crystal　to　date.　Our　research　not　only　confirms　the　potential　of　tellurite-selenite　systems　in　the　field　of　birefringent　materials,　but　also　opens　up　new　possibilities　for　the　development　of　future　optical　materials.　©　2025　The　Royal　Society　of　Chemistry.