A novel morphology of Bi2O3 nanomaterial (nanosquaresheets) has been successfully synthesized in large area by thermal evaporation of commercial Bi2O3 powder at high temperatures. The Bi2O3 nanosquaresheets (NSSs) are perfect regular squares and have sharp, uniform edges. The typical length of the sides is in the range of 200–600 nm. The thickness varies from 30 to 100 nm. Electron microscopy observations show that the Bi2O3 NSSs are single crystalline. The growth of Bi2O3 NSSs is probably controlled by a vapor–solid mechanism. The dominate growth directions are [2̄10] and [1̄2̄2] within the (245) planes.