Josiah Royce (/rɔɪs/; November 20, 1855 – September 14, 1916) was an American pragmatist and objective idealist philosopher and the founder of American idealism. His philosophical ideas included his joining of pragmatism and idealism, his philosophy of loyalty, and his defense of absolutism.

Royce's essay "A Word for the Times" (1914) was quoted in the 1936 State of the Union Address by Franklin Delano Roosevelt: "The human race now passes through one of its great crises. New ideas, new issues – a new call for men to carry on the work of righteousness, of charity, of courage, of patience, and of loyalty. [...] I studied, I loved, I labored, unsparingly and hopefully, to be worthy of my generation."

Royce, born on November 20, 1855, in Grass Valley, California, was the son of Josiah and Sarah Eleanor (Bayliss) Royce, whose families were recent English emigrants and who sought their fortune in the westward movement of the American pioneers in 1849. In 1875 he received a B.A. from the University of California, Berkeley (which moved from Oakland to Berkeley during his matriculation), where he later accepted an instructorship teaching English composition, literature, and rhetoric.

While at the university, he studied with Joseph LeConte, Professor of Geology and Natural History and a prominent spokesperson for the compatibility between evolution and religion. In a memorial published shortly after LeConte's death, Royce described the impact of LeConte's teaching on his own development, writing: "the wonder thus aroused was, for me, the beginning of philosophy" (p. 328). After studying logic under Hermann Lotze at the University of Göttingen, he returned to the United States to finish his doctorate at Johns Hopkins University, where he was awarded one of the institution's first four doctorates, in philosophy in 1878. At Johns Hopkins he taught a course on the history of German thought, which was “one of his chief interests” because he was able to give consideration to the philosophy of history. After four years at the University of California, Berkeley, he went to Harvard in 1882 as a sabbatical replacement for William James, who was Royce's friend and philosophical antagonist. Royce's position at Harvard was made permanent in 1884, and he remained there until his death on September 14, 1916.

Royce was an elected member of the American Academy of Arts and Sciences, the United States National Academy of Sciences, and the American Philosophical Society.

Royce stands out starkly in the philosophical crowd because he was the only major American philosopher who spent a significant period of his life studying and writing history, specifically of the American West.^{[citation needed]} “As one of the four giants in American philosophy of his time […] Royce overshadowed himself as historian, in both reputation and output” (Pomeroy, 2). During his first three years at Harvard, Royce taught many different subjects such as English composition, forensics, psychology and philosophy for other professors. Although he eventually settled into writing philosophy, his early adulthood was characterized by wide-ranging interests, during which he wrote a novel, investigated paranormal phenomena (as a skeptic), and published a significant body of literary criticism. Only as historian and philosopher did he distinguish himself. Royce spread himself too thin, however, and in 1888 suffered a nervous breakdown which required him to take a leave of absence from his duties.

John Clendenning's 1999 book is the standard biography of Royce. Autobiographical remarks by Royce can be found in Oppenheim's study. In 1883 Royce was approached by a publishing company who asked him to write the state history of California, “In view of his precarious circumstances at Harvard and his desire to pursue the philosophical work for which he had come east, Royce found the prospect attractive […]. He wrote to a friend that he was ‘tempted by the money’”. Royce viewed the task as a side project, which he could use to fill his free time. In 1891 his historical writing career came to an end, but not before he had published several reviews of California’s historical volumes, and articles in journals to supplement his history. Royce is also mentioned in the book The Unseen Guest by Joan Darby.

The years between 1882 and 1895 established Royce as one of the most eminent American philosophers. His publication in 1885 of The Religious Aspect of Philosophy, and in 1892 of The Spirit of Modern Philosophy, both based on Harvard lectures, secured his place in the philosophical world. The former of these contained a new proof for the existence of God based upon the reality of error. All errors are judged to be erroneous in comparison to some total truth, Royce argued, and we must either hold ourselves infallible or accept that even our errors are evidence of a world of truth. Having made it clear that idealism depends upon postulates and proceeds hypothetically, Royce defends the necessity of objective reference of our ideas to a universal whole within which they belong, for without these postulates, "both practical life and the commonest results of theory, from the simplest impressions to the most valuable beliefs, would be for most if not all of us utterly impossible".