The molecular beam epitaxy (MBE) process is generally surrounded by liquid nitrogen (LN2) cooled surfaces for optimum control of the environment in which the thin‐film deposition takes place. The design and operation of a LN2supply system for feeding the cryogenicly cooled surfaces in a MBE system is described here. The supply system is based on modification of a standard 50‐lLN2storage dewar. The reservoir gravity feeds liquid through a vacuum‐insulated line into the fill port of the MBE system. A solenoid‐operated vent valve activated by a temperature controller regulates the level of LN2in the MBE system. The LN2supply system is efficient and costs much less than other alternatives.