The first bismuth borosulfate (H 3 O)Bi[B(SO 4) 2 ] 4 is only the second featuring a three-dimensional anion, the first tectosilicate-analogous borosulfate synthesised solvothermally without a precursor (from Bi(NO 3) 3 •5 H 2 O and B(OH) 3 in oleum); moreover, it is the first comprising two differently charged cations and crystallises in a new structure type in space group I4 (no. 82) (a = 11.857(1), c = 8.149(1) , 1947 refl., 111 param., wR2 = 0.037), confirmed by a second harmonic generation (SHG) measurement. The B(SO 4) 4 supertetrahedra are connected via all four sulfate tetrahedra resulting in a threedimensional anion with both H 3 O + and Bi 3+ cations in channels. Additionally, the crystal structure of a further bismuth borosulfate, Bi 2 [B 2 (SO 4) 6 ], is elucidated crystallising isotypically to the rare-earth borosulfates R 2 [B 2 (SO 4) 6 ] in space group C2/c (No. 15) (a = 13.568(2), b = 11.490(2), c = 11.106(2) , 3127 refl., 155 param., wR2 = 0.035). Moreover, the optical and thermal properties of both compounds are discussed.