Human nature is a concept that denotes the fundamental dispositions and characteristics—including ways of thinking, feeling, and acting—that humans are said to have naturally. The term is often used to denote the essence of humankind, or what it 'means' to be human. This usage has proven to be controversial in that there is dispute as to whether or not such an essence actually exists.

Arguments about human nature have been a central focus of philosophy for centuries and the concept continues to provoke lively philosophical debate. While both concepts are distinct from one another, discussions regarding human nature are typically related to those regarding the comparative importance of genes and environment in human development (i.e., 'nature versus nurture'). Accordingly, the concept also continues to play a role in academic fields, such as both the natural and the social sciences, and philosophy, in which various theorists claim to have yielded insight into human nature. Human nature is traditionally contrasted with human attributes that vary among societies, such as those associated with specific cultures.

The concept of nature as a standard by which to make judgments is traditionally said to have begun in Greek philosophy, at least in regard to its heavy influence on Western and Middle Eastern languages and perspectives. By late antiquity and medieval times, the particular approach that came to be dominant was that of Aristotle's teleology, whereby human nature was believed to exist somehow independently of individuals, causing humans to simply become what they become. This, in turn, has been understood as also demonstrating a special connection between human nature and divinity, whereby human nature is understood in terms of final and formal causes. More specifically, this perspective believes that nature itself (or a nature-creating divinity) has intentions and goals, including the goal for humanity to live naturally. Such understandings of human nature see this nature as an "idea", or "form" of a human. However, the existence of this invariable and metaphysical human nature is subject of much historical debate, continuing into modern times.

Against Aristotle's notion of a fixed human nature, the relative malleability of man has been argued especially strongly in recent centuries—firstly by early modernists such as Thomas Hobbes, John Locke and Jean-Jacques Rousseau. In his Emile, or On Education, Rousseau wrote: "We do not know what our nature permits us to be." Since the early 19th century, such thinkers as Hegel, Darwin, Freud, Marx, Kierkegaard, Nietzsche, and Sartre, as well as structuralists and postmodernists more generally, have also sometimes argued against a fixed or innate human nature.

Charles Darwin's theory of evolution has particularly changed the shape of the discussion, supporting the proposition that mankind's ancestors were not like mankind today. As in much of modern science, such theories seek to explain with little or no recourse to metaphysical causation. They can be offered to explain the origins of human nature and its underlying mechanisms, or to demonstrate capacities for change and diversity which would arguably violate the concept of a fixed human nature.