Ross Henry Day was an Australian experimental psychologist well known for his research on visual illusions and for his critical role in the establishment of experimental psychology in Australia. This role began with his creation of Australia’s first department of experimental psychology at Monash University in 1965. He also played a leading role in the formation of the Australian Psychological Society in 1966, and in the introduction to Australia of the study of human factors in engineering and ergonomics. He was the first psychologist to be elected Fellow of the Australian Academy of Science.