E.U. Condon’s major contributions were in atomic and molecular physics and spectroscopy; his book with G.H. Shortley on The Theory of Atomic Spectra dominated the field of spectroscopy for half a century and remains an invaluable reference. He also played an important role in the institutions of American science. He served for many years as the editor of Reviews of Modern Physics, and with Hugh Odishaw he edited the still widely used Handbook of Physics. After World War II, Condon became director of the National Bureau of Standards (now NIST), and helped to make it one of the premier research laboratories in the physical sciences in the world. The Selected Scientific Papers reprint many of the most important contributions Condon made to atomic physics, quantum theory, nuclear physics, condensed-matter physics and other fields. The Selected Popular Writings contain articles he wrote on technical topics for such journals as The American Journal of Physics, Science, and Nature, as well as reflections on education, UFO’s, and other topics.