Two novel complex oxonium bromoselenates(II,IV) and Ϫ(II) are reported containing [H 3 O] ϩ and [H 5 O 2 ] ϩ cations coordinated by crown ether ligands. [H 3 O(dibromo-benzo-18-crown-6)] 2 [Se 3 Br 10 ] (1) and [H 5 O 2 (bis-dibromo-dibenzo-24-crown-8] 2 [Se 3 Br 8 ] (2) were prepared as dark red crystals from dichloromethane or acetonitrile solutions of selenium tetrabromide, the corresponding unsubstituted crown ethers, and aqueous hydrogen bromide. The products were characterized by their crystal structures and by vibrational spectra.