Chalmers Ashby Johnson (August 6, 1931 – November 20, 2010) was an American author and professor emeritus of the University of California, San Diego. He served in the Korean War, was a consultant for the CIA from 1967 to 1973, and chaired the Center for Chinese Studies at the University of California, Berkeley from 1967 to 1972. He was also president and co-founder with Steven Clemons of the Japan Policy Research Institute (now based at the University of San Francisco), an organization promoting public education about Japan and Asia.
Johnson wrote numerous books including three examinations of the consequences of American Empire: Blowback, The Sorrows of Empire, and Nemesis; The Last Days of the American Republic. A former cold warrior, he feared that, "A nation can be one or the other, a democracy or an imperialist, but it can't be both. If it sticks to imperialism, it will, like the old Roman Republic, on which so much of our system was modeled, lose its democracy to a domestic dictatorship."