Cognitive inertia is the tendency – for a particular orientation in an individual's thinking about a matter, belief, or strategy – to resist change. Clinical and neuroscientific literature often describes it as a lack of motivation to generate cognitive processes needed to attend to a matter or problem.

The physics term "inertia" emphasizes resistance to change in a mode of cognitive processing that has been used for a substantial time. Commonly confused with belief perseverance, cognitive inertia is perseverance in an interpretation of information, not perseverance in the belief itself.

Cognitive inertia has been causally implicated in disregard of impending threats to one's health or environment, in enduring political values, and in deficits in task switching. Interest in the phenomenon was taken up by economic and industrial psychologists primarily to explain resistance to change in brand loyalty, in group brainstorming, and in business strategizing. 

In a clinical setting, cognitive inertia has been used as a diagnostic tool for neurodegenerative diseases, depression, and anxiety.

Critics have commented that the term "cognitive inertia" oversimplifies resistant thought processes and suggest a more integrative approach involving motivation, emotion, and developmental factors.

The idea of cognitive inertia has its roots in philosophical epistemology. Early allusions to a reduction of cognitive inertia can be found in the Socratic dialogues written by Plato. Socrates builds his argument by using the detractor's beliefs as the premise of his argument's conclusions. In doing so, Socrates reveals the detractor's fallacy of thought, inducing the detractor to change their mind or face the reality that their thought processes are contradictory. Ways to combat persistence of cognitive style are also seen in Aristotle's syllogistic method which employs logical consistency of the premises to convince an individual of the conclusion's validity.

At the beginning of the twentieth century, two of the earliest experimental psychologists, Müller and Pilzecker, defined perseveration of thought to be "the tendency of ideas, after once having entered consciousness, to rise freely again in consciousness". Müller described perseveration by illustrating his own inability to inhibit old cognitive strategies with a syllable-switching task, while his wife easily switched from one strategy to the next. One of the earliest personality researchers, W. Lankes, more broadly defined perseveration as "being confined to the cognitive side" and possibly "counteracted by strong will". These early ideas of perseveration were the precursor to how the term cognitive inertia would be used to study certain symptoms in patients with neurodegenerative disorders, rumination and depression.  

Originally proposed by William J. McGuire in 1960, the theory of cognitive inertia was built upon emergent theories in social psychology and cognitive psychology that centered around cognitive consistency, including Fritz Heider's balance theory and Leon Festinger's cognitive dissonance. McGuire used the term cognitive inertia to account for an initial resistance to change how an idea was processed after new information, that conflicted with the idea, had been acquired.