Wilhelm Maximilian Wundt (16 August 1832 - 31 August 1920) was a German medical doctor, psychologist, physiologist, philosopher, and professor, known today as one of the founding figures of modern psychology. He is widely regarded as the "father of experimental psychology". In 1879, Wundt founded one of the first formal laboratories for psychological research at the University of Leipzig.

By creating this laboratory he was able to explore the nature of religious beliefs, identify mental disorders and abnormal behavior, and map damaged areas of the human brain. By doing this he was able to establish psychology as a separate science from other topics. He also formed the first journal for psychological research in 1881.

Wundt was born at Neckarau, Baden, in 1832 (now part of Mannheim), the fourth child to parents Maximilian Wundt (a Lutheran minister), and his wife Marie Frederike. He studied from 1851 to 1856 at the University of Tübingen, University of Heidelberg, and the University of Berlin. After graduating in medicine from Heidelberg (1856), Wundt studied briefly with Johannes Peter Müller, before joining the University's staff, becoming an assistant to the physicist and physiologist Hermann von Helmholtz in 1858. There he wrote Contributions to the Theory of Sense Perception (1858-62).

He married Sophie Mau while at Heidelberg. It was during this period that Wundt offered the first course ever taught in scientific psychology, all the while stressing the use of experimental methods drawn from the natural sciences, emphasizing the physiological relationship of the brain and the mind. His background in physiology would have a great effect on his approach to the new science of psychology. His lectures on psychology were published as Lectures on the Mind of Humans and Animals in 1863. He was promoted to Assistant Professor of Physiology at Heidelberg in 1864. Weber (1795-1878) and Fechner (1801-1887), who worked together at Leipzig, inspired Wundt's interest in physiological psychology.

Wundt applied himself to writing a work that came to be one of the most important in the history of psychology, Principles of Physiological Psychology in 1874. The Principles utilized a system of psychology that sought to investigate the immediate experiences of consciousness, including feelings, emotions, volitions and ideas, mainly explored through Wundt's system of "internal perception", or the self-examination of conscious experience by objective observation of one's consciousness.

Parts of Wundt's system were developed and championed by his one-time student, Titchener, who described his system as "Structuralism". Several of Wundt's works, including Principles of Physiological Psychology are considered fundamentally important texts in the field of psychology. Though widely recognized as important in the birth and growth of psychology, his influence in psychology today is a subject of debate among experts.

Though Wundt wrote extensively on a variety of subjects, including philosophy, physics, physiology, and of course psychology, the immensity of his collected writings and the 65 year-long duration of his career makes it difficult to identify a single, coherent mode of thought. Wundt is argued by some writers to have been a devout foundationalist, working tirelessly to understand the intricacies of the areas of knowledge he studied to form a coherent, atomistic understanding of the universe. In recognition of Wundt's work, the American Psychological Association established the "Wilhelm Wundt-William James Award for Exceptional Contributions to Trans-Atlantic Psychology", which recognizes "a significant record of trans-Atlantic research collaboration."

Several of Wundt's students became eminent psychologists in their own right. They include: the German Oswald Külpe (a professor at the University of Würzburg); the Americans James McKeen Cattell (the first professor of psychology in the United States), G. Stanley Hall (the father of the child psychology movement and adolescent developmental theorist, head of Clark University), Charles Hubbard Judd (Director of the School of Education at the University of Chicago), Hugo Münsterberg (who contributed to the development of industrial psychology and taught at Harvard University), Edward Bradford Titchener (who founded the first psychology laboratory in the United States at Cornell University), Lightner Witmer (founder of the first psychological clinic in his country); the Englishman Charles Spearman (who developed the two-factor theory of intelligence and several important statistical analyses - Factor analysis, Spearman's rank correlation coefficient); the Romanian Constantin Rădulescu-Motru (Personalist philosopher and head of the Philosophy department at the University of Bucharest).

Wundt's laboratory students called their approach Ganzheit Psychology ("holistic psychology") following Wundt's death. Much of Wundt's work was derided mid-century in the United States because of a lack of adequate translations, misrepresentations by certain students, and behaviorism's polemic with the structuralist program. Titchener, a two-year resident of Wundt's lab and one of Wundt's most vocal advocates in the United States, is responsible for several English translations and mistranslations of Wundt's works that supported his own views and approach, which he termed "structuralism" and claimed was wholly consistent with Wundt's position. Titchener's focus on internal structures of mind was rejected by behaviorists following the ideas of B.F. Skinner; the latter dominated psychological studies in the mid-1900s. Part of this rejection included Wundt, whose work was eclipsed during this period. In later decades, his actual positions and techniques have seen reconsideration and reassessment by major psychologists.

An optical illusion described by him is called the Wundt illusion.