George Sidney Brett (August 5, 1879 in Briton Ferry, Wales — October 27, 1944 in Toronto, Canada) was an English-Canadian psychologist. Brett's main contribution to psychology was his 3-volume History of Psychology (1912–1921), which was the first history of psychology written in the English language, pre-dating Edwin Boring's canonical History of Experimental Psychology (1929). Brett's text assesses the philosophy of mind theories of the time and presents psychology as the study of the immediate data of the inner life, distinguishes it from other sciences, and resists the new experimentalist approach.