Gestalt psychology, or gestaltism, is a school of thought originating from the Berlin School of Experimental Psychology in the early 20th century that studies how people acquire and maintain meaningful perceptions out of an apparently chaotic sensory world.

Its central claim is that the mind forms a global, self-organizing whole from perceptual input, rather than assembling perception piece by piece from independent parts — captured in the school's signature idea that "the whole is different from the sum of its parts." The physiological mechanisms proposed to underlie this organizing tendency have never been well defined, and empirical support for them remains thin, which has kept Gestalt theory more influential as a perceptual framework — shaping later work in design, visual perception, and cognitive psychology — than as a settled neuroscientific model.