Warren Sturgis McCulloch (November 16, 1898 – September 24, 1969) was an American neurophysiologist and cybernetician known for his work on the foundation for certain brain theories and his contribution to the cybernetics movement. Along with Walter Pitts, McCulloch created computational models based on mathematical algorithms called threshold logic which split the inquiry into two distinct approaches, one approach focused on biological processes in the brain and the other focused on the application of neural networks to artificial intelligence.

Warren Sturgis McCulloch was born in Orange, New Jersey, in 1898. His brother was a chemical engineer and Warren was originally planning to join the Christian ministry. As a teenager he was associated with the theologians Henry Sloane Coffin, Harry Emerson Fosdick, Herman Karl Wilhelm Kumm and Julian F. Hecker. He was also mentored by the Quaker Rufus Jones. He attended Haverford College then studied philosophy and psychology at Yale University, where he received a Bachelor of Arts degree in 1921. He continued to study psychology at Columbia and received a Master of Arts degree in 1923. Receiving his MD in 1927 from the Columbia University College of Physicians and Surgeons in New York, he undertook an internship at Bellevue Hospital, New York. Then he worked under Eilhard von Domarus at the Rockland State Hospital for the Insane. He returned to academia in 1934. He worked at the Laboratory for Neurophysiology at Yale University from 1934 to 1941.

In 1941 he moved to Chicago and joined the Department of Psychiatry at the University of Illinois at Chicago, where he was a professor of psychiatry, as well as the director of the Illinois Neuropsychiatric Institute until 1951. From 1952 he worked at the Massachusetts Institute of Technology in Cambridge, Massachusetts with Norbert Wiener. He was a founding member of the American Society for Cybernetics and its second president during 1967–1968. He was a mentor to the British operations research pioneer Stafford Beer.

McCulloch had a range of interests and talents. In addition to his scientific contributions he wrote poetry (sonnets), and he designed and engineered buildings and a dam at his farm in Old Lyme, Connecticut.

McCulloch married Ruth Metzger, known as 'Rook', in 1924 and they had three children. He died in Cambridge in 1969.

He is remembered for his work with Joannes Gregorius Dusser de Barenne from Yale and later with Walter Pitts from the University of Chicago. He provided the foundation for certain brain theories in a number of classic papers, including "A Logical Calculus of the Ideas Immanent in Nervous Activity" (1943) and "How We Know Universals: The Perception of Auditory and Visual Forms" (1947), both published in the Bulletin of Mathematical Biophysics. The former is "widely credited with being a seminal contribution to neural network theory, the theory of automata, the theory of computation, and cybernetics".

McCulloch was the chair of the set of Macy conferences dedicated to Cybernetics. These, greatly due to the diversity of the backgrounds of the participants McCulloch brought in, became the foundation for the field.

In Wiener's Cybernetics (1948), he recounted an event in the spring of 1947, when McCulloch designed a machine to allow the blind to read, by converting printed letters to tones. He designed it so that the tone is invariant for the same letter viewed under different angles. Gerhardt von Bonin saw the design, and immediately asked, " Is this a diagram of the fourth layer of the visual cortex of the brain?".