A compound carbon thermometer consisting of an abreast connection of a carbon Speer resistor and a carbon Allen‐Bradley resistor was tested in the temperature interval 0.3–100 K, an interval which generally requires two independent resistors to be covered. The characteristics, sensitivity, and analytical handling of the resistance versus temperature data are discussed and compared with the corresponding behavior of other thermometers. The satisfactory performance of the compound carbon device contributes to the extension of wide‐range thermometry to 0.3 K.