A compact heater, designed for the deposition of thin films at high temperatures in an oxidizing atmosphere or in vacuum, is described. The heater, including an oxygen‐resistant case and the attached substrate, can be loaded into a vacuum deposition chamber through a small‐diameter load‐lock port, and will operate in 0–1 atm of oxygen at temperatures up to at least 800 °C. Heat is generated resistively, and the substrates are heated directly by thermal conduction. The heater was built specifically to heat substrates during the growth of high‐temperature superconducting thin films.