It was discovered in 1860 by Kirchhoff and Bunsen while examining the residues that were obtained by evaporation of mineral waters. The new bright lines in the blue region were attributed to a new element - given the name cesium for the Latin caesius - sky blue.

Extraction of cesium compounds by Bunsen involved concentration of the cesium and other impurities by evaporation of large volumes of mineral water. Bunsen prepared chlorides, carbonates and other salts of cesium. He studied the properties of these salts and attempted to prepare cesium metal but was unsuccessful. The metal was first obtained by Setterburg in 1882 by electrolysis of a cesium cyanide-barium cyanide melt.

Cesium had no significant industrial application until 1926 when the metal was used as a getter and an effective means for reducing the electron work function on coated tungsten filaments in radio tubes.