An Essay Concerning Human Understanding is one of John Locke's two most famous works, the other being his Second Treatise on Civil Government. Written in 1690, the essay concerns the foundation of human knowledge and understanding. He describes the mind at birth as a blank sheet, or tabula rasa, being filled later through experiences. The essay contributed to the growth of rationalism in the 18th century, and influenced philosophers such as Hume and Kant.

New Essays on Human Understanding, a chapter-by-chapter rebuttal of the book was written by Gottfried Leibniz, the same year as Locke's death.