George Trumbull Ladd (19 January 1842 – 8 August 1921) was an American philosopher and psychologist.
Born in Painesville, Lake County, Ohio, he graduated from Western Reserve College in 1864 and from Andover Theological Seminary in 1869; he preached in Edinburg, Ohio, during 1869 to 1871, and in the Spring Street Congregational Church of Milwaukee from 1871 to 1879; and was professor of philosophy at Bowdoin College from 1879 to 1881, and Clark professor of metaphysics and moral philosophy at Yale from 1881 until 1901, when he took charge of the graduate department of philosophy and psychology; he became professor emeritus in 1905.
During 1879 to 1882 he lectured on theology at Andover Theological Seminary, and in 1883 at Harvard, where during 1895 to 1896 he conducted a graduate seminar in ethics. He lectured in Japan in 1892 and 1899 (when he also visited the universities of India) and from 1906 to 1907. He was much influenced by the German philosopher Lotze, whose Outlines of Philosophy he translated (6 vols., 1877) and was one of the first to introduce (1879) the study of experimental psychology into America; the Yale psychological laboratory being founded by him.