Two new alkaline-earth-metal fluoroiodate compounds, BaI2O5F2 and BaIO2F3, were successfully synthesized by replacing the O atoms in the iodates with F atoms via the hydrothermal method. They crystallize in centrosymmetric space groups P2(1)/c and Cmca, respectively. Both compounds possess large birefringences (Delta n) of 0.174 at 1064 nm for BaI2O5F2 and 0.133 at 1064 nm for BaIO2F3. Structurally, BaI2O5F2 has a large birefringence due to the highly polarizable [IO3F](2-) with high anisotropic polarizability; for BaIO2F3, owing to the regulation of cationic polyhedra, the arrangement of [IO2F2](-) anionic groups is well-ordered, and it exhibits large anisotropy. Also, both compounds exhibit a short UV cutoff edge, 230 and 234 nm, respectively. These results demonstrate that the two new alkaline-earth-metal fluoroiodate compounds will have potential applications as UV birefringent materials.