Tyler Dennett (June 13, 1883, Spencer, Wisconsin – December 29, 1949) was an American historian and educator. He is best known for his book John Hay (1933), for which he won the 1934 Pulitzer Prize for biography.
In 1900, Dennett enrolled at Bates College, then transferred to Williams College as a sophomore. After his graduation in the spring of 1904 and a year of work in Williamstown, Massachusetts he attended the Union Theological Seminary, where he was awarded a diploma in 1908. He served briefly as a Congregational Minister, but soon left to pursue a career in journalism. In 1922 he published Americans in Eastern Asia, a study of American policy in the Far East, which was well received and was long held as an important work in the field. Dennett published "President Roosevelt's Secret Pact with Japan" in 1924, which came to be known as the Taft–Katsura Agreement. This paper put forth that formerly isolationist Japan and the US began to carve up their sphere's of influence (that would later become world empires) with this agreement, and it was therefore of first class importance historically. Later historians questioned this interpretation.