For the mass production of astatine-211, a promising radiopharmaceutical for cancer treatment, the National Institute for Quantum and Radiological Science and Technology has proposed the innovative “Liquid Bismuth Target System.” The target window in this system must be made from a material that resists the highly corrosive liquid bismuth environment. To meet this requirement, a promising target window material was selected in corrosion experiments performed in stagnant liquid bismuth. Based on knowledge of corrosion in liquid lead–bismuth eutectic gained during the development of fast reactors and accelerator-driven subcritical systems, FeCrMo–alloy, FeCrAl–alloy, and austenitic stainless steel (as a reference) were selected as the specimen materials. Experiments were carried out under saturated dissolved oxygen and low oxygen conditions, and the corrosion behaviors of the specimens were evaluated, mainly by scanning electron microscopy. The FeCrAl–alloy exhibited the most excellent corrosion resistance, followed by FeCrMo–alloy. Both materials are suitable candidates for the target window. Although austenitic stainless steel was less corrosion resistant than the former two materials, it is a likely applicable for the target window under appropriately limited operation conditions (such as irradiation current and exposure time) of the liquid bismuth target system.