A mindset (also known as mentality especially when considered as biased and closed-minded) refers to an established set of attitudes of a person or group concerning culture, values, philosophy, frame of reference, outlook, or disposition. It may also develop from a person's worldview or beliefs about the meaning of life.

A mindset could create an incentive to adopt (or accept) previous behaviors, choices, or tools, sometimes known as cognitive inertia or groupthink. When a prevailing mindset is limiting or inappropriate, it may be difficult to counteract the grip of mindset on analysis and decision-making.

In cognitive psychology, mindset is the cognitive process activated in a task. In addition to the field of cognitive psychology, the study of mindset is evident in the social sciences and other fields (such as positive psychology). Characteristic of this area of study is its fragmentation among academic disciplines.

Numerous scholars have identified mindset history as being a critical gap in contemporary literature and also in current approaches to mindset education and training.

Mindset research is an interdisciplinary field of inquiry. Some of the earliest studies to explicitly include mindset as an area of focus were conducted in the 1910s and 1920s, primarily within a psychology and education context. This includes studies by scholars including Thaddeus Lincoln Bolton (1909), Edward Kellogg Strong and Margaret Hart Strong (1913), Edward Lee Thorndike (1913), Alexander James Inglis (1918), William Heard Kilpatrick (1921), and more.

Between the 1980s and 2000s, mindset research and its applications began to expand into other areas, including Glen Fisher's (1988) studies in international relations, Ellen Langer's (1989) research on mindfulness, Peter Gollwitzer's (1989) psychology of action phases,, Donella Meadows' (1991) theory of systems change, Stephen Rhinesmith's (1992) work on global mindsets, Ronald Heifetz's (1994) practice of adaptive leadership, Carol Dweck's (2006) concept of implicit theories, and Robert Kegan's and Lisa Lahey's (2009) theory of adult development.

A political example is the "Cold War mindset" in the U.S. and the USSR. This mindset reflects how people globally perceived the levels of security between the two nations. This mindset suggested that if one nation grew in strength and power, the other was threatened and vice versa. The main goal of the Cold War Mindset was to strengthen one's own nation's military and alliances while keeping the other nation's power limited. Also included in this mindset is the belief in game theory, in a chain of command in control of nuclear materials, and in the mutual assured destruction of both in a nuclear war. This mindset prevented an attack by either country, but deterrence theory has made assessments of the Cold War mindset a subject of controversy.

Modern military theory attempts to challenge entrenched mindsets in asymmetric warfare, terrorism, and the proliferation of weapons of mass destruction. These threats are "a revolution in military affairs", requiring rapid adaptation to new threats and circumstances.