We report the unexpectedly excellent dielectric properties of amorphous thin films with compositions in the Bi–Ti–O system. Films were deposited by RF magnetron reactive co-sputtering. In the composition range of 0.5 < $x$ < 0.7, amorphous ${{\text{Bi}}_{1-}}_x$${\text{Ti}}_x$${\text{O}}_y$ exhibits excellent dielectric properties, with a high dielectric constant, ${𝜀}_r$$\sim$ 53, and a dissipation factor as low as tan $\delta$ = 0.007. The corresponding maximum breakdown field reaches $\sim$1.6 MV/cm, yielding a maximum stored charge per unit area of up to 8 $\mu$C/cm². This work demonstrates the potential of amorphous Bi–Ti–O as a high-performance thin-film dielectric material that is compatible with high-performance integrated circuits.We report the unexpectedly excellent dielectric properties of amorphous thin films with compositions in the Bi–Ti–O system. Films were deposited by RF magnetron reactive co-sputtering. In the composition range of 0.5 < $x$ < 0.7, amorphous ${{\text{Bi}}_{1-}}_x$${\text{Ti}}_x$${\text{O}}_y$ exhibits excellent dielectric properties, with a high dielectric constant, ${𝜀}_r$$\sim$ 53, and a dissipation factor as low as tan $\delta$ = 0.007. The corresponding maximum breakdown field reaches $\sim$1.6 MV/cm, yielding a maximum stored charge per unit area of up to 8 $\mu$C/cm². This work demonstrates the potential of amorphous Bi–Ti–O as a high-performance thin-film dielectric material that is compatible with high-performance integrated circuits.