William Savage Johnson was born in Portsmouth, Ohio to Sherman Gilbert and Emily Harriet (Savage) Johnson. He was educated in the classics and Latin and Greek before intensifying his study of English Literature while at graduate school at Yale University, from which he earned his doctorate in 1905.

Johnson remained at Yale for three years as an instructor in the English Department before moving to Lawrence, Kansas to teach at the University of Kansas. While at KU, Johnson achieved full professorship status in 1920 and served as department chairman for the English Department for 16 years, from 1924 to 1940.

Johnson had a wide variety of scholarly interests and published on several different themes and authors, including Thomas Carlyle, Ben Jonson, Alfred Lord Tennyson, Kansas-based poetry, Matthew Arnold, and Robinson Jeffers. This included book-length works as well as shorter articles. Late in his career, he focused primarily in contemporary British and American poets, and the Irish writer A.E., or George William Russell (1867-1935), became one of Johnson's lifelong friends. Through Russell, Johnson met William Butler Yeats, and otherwise, Johnson interacted with a variety of British and American poets of his era.

While Johnson won the Albert S. Cook poetry prize while he was a student at Yale, he only dabbled with writing poetry himself. Some of his poems were published during his lifetime, and several more poems were published posthumously.

William Savage Johnson married Claudia Clara Pendleton in 1920. Claudia Pendleton Johnson had graduated from the Univerity of Kansas in 1908. The Johnsons gave a variety of rare books and manuscripts to the University of Kansas Libraries, and in 1964 the reading room for the Special Collections Department at Watson Library was named in honor of William Johnson. A classroom at the Kenneth Spencer Research Library was later named for him after Special Collections moved to the new building in 1968.