Ken'ichi Watanabe was Professor of Physics at the University of Hawai'i at Manoa from 1954 until his untimely death in 1969. Born in Honolulu, he was educated in Hawaii's public schools from where he matriculated at the California Institute of Technology and received his PhD in physics in 1940.

Until 1948 he taught mathematics and physics, first at the Univerisity of Hawai'i and later at Wabash College. In 1948 he joined the staff of the US Naval Research Laboratory as a physicist, and in 1951 became head of Atmospheric Composition section of the Air Force Cambridge Research Center. At the Naval Research Laboratory he pioneered in the study of the upper atmosphere by use of rockets and his work on measurement of ozone concentrations in the upper atmosphere is well known. At the Air Force Cambridge Research Center he and his co-workers (Inn and Zelikoff) were the first, in 1953, to measure and publish in detail the absorption coefficients of several important upper atmospheric gasses in the vacuum ultraviolet region.

In 1954 he returned to the University of Hawaii as professor of physics and established a vacuum ultraviolet spectroscopy laboratory. Together with his graduate students, he obtained the ionization potentials and absorption cross sections of hundreds of molecules and atoms. In 1961 he was promoted to Senior Professor of Physics and in the spring of 1969 received the University's award for excellence in research. Watanabe was a fellow of the American Physical Society and of the American Optical Society, a member of the NASA Planetary Atmospheres Panel and of the editorial advisory board of the Planetary and Space Science Journal.

Watanabe Hall, on the campus of the University of Hawai'i at Manoa was named in memory of Professor Ken'ichi Watanabe (1910-1969).