Recent theoretical studies revealed that two-dimensional (2D) antimonene has attractive characteristics, such as superior photothermal conductivity, absorption over a wide range, high mobility, and good spintronic properties. Herein, we report a reliable liquid phase exfoliation (LPE) route for the preparation of high-quality high-stability atomically thin (AT) antimonene via high ultrasonic power. The AT antimonene delivers a high specific capacity of up to 860 mA·h·g^–1, with high rate capability and good cycling stability as an anode of a sodium ion battery (SIB). The good conductivity and 2D structure endow AT antimonene with more active sites for sodium storage, a facilitated pathway for electron transfer and mass transport, and the capability to reduce the volume expansion during the discharge–charge process.