William Warren Bartley, III (October 2, 1934 – February 5, 1990), known as W.W. Bartley, III, was an American philosopher.
After his doctoral graduation, Bartley worked as a lecturer in logic in London. Later, he held positions at the Warburg Institute and the University of California, San Diego. He was appointed to his first full professorship in 1969, at the University of Pittsburgh, where he had been teaching since 1963.
In 1973 he joined the California State University, Hayward faculty as a Professor of Philosophy, where he received the distinction of “Outstanding Professor” of the entire California State University System in 1979. His last position was that of a Senior Research Fellow at the Hoover Institution.