Malingering is the intentional fabrication, feigning, or exaggeration of physical or psychological symptoms to obtain an external benefit, such as personal gain, relief from duty or work, avoidance of arrest, acquisition of medication, or mitigation of criminal sentencing.

Although malingering is not a medical diagnosis, it may be recorded as a "focus of clinical attention" or a "reason for contact with health services". It is coded in both the ICD-10 and DSM-5. Motivations vary- for example, some homeless individuals may feign mental illness to gain hospital admission. Failure to detect malingering can have significant consequences for insurance systems, healthcare institutions, public safety, and veterans' disability programs. Malingered behaviour typically ceases once the desired external goal is achieved.

Malingering is distinct from other forms of excessive illness behaviour. In somatic symptom disorder, symptoms arise from psychological causes but are experienced as real; in factitious disorder, symptoms are intentionally produced but not for external gain. Both conditions are recognised as diagnosable mental disorders in the DSM-5; however, some clinicians question the clarity of these distinctions. The phrase "feigned madness" is commonly used to describe the deliberate simulation of mental illness for purposes of evasion, deception, or diverting suspicion. Historically, this strategy has also been employed- sometimes formally, as with court jesters, to grant individuals license to speak uncomfortable or socially prohibited truths.

According to 1 Samuel in the Old Testament, King David feigned madness to Achish, the king of the Philistines. Some scholars believe this was not feigned but real epilepsy, and phrasing in the Septuagint supports that position. Odysseus was said to have feigned insanity to avoid participating in the Trojan War. In China's Warring States period, military strategist Sun Bin, while imprisoned by his rival Pang Juan in the state of Wei, feigned madness to get Pang to release him, and eventually escaped back to his native Qi. Eventually, he led Qi troops to defeat Wei troops at the Battle of Maling, leading Pang to suicide.

Malingering was recorded in Roman times by the physician Galen, who reported two cases: one patient simulated colic to avoid a public meeting, and another feigned an injured knee to avoid accompanying his master on a long journey. Lucius Junius Brutus, who feigned stupidity, causing the Tarquins to underestimate him as a threat until the time when he was able to drive the Roman people to insurrection. Ibn al-Haytham, also known as Alhazen, who was ordered by the sixth Fatimid Caliph, al-Hakim, to regulate the flooding of the Nile; he later perceived the insanity and futility of what he was attempting to do and, fearing for his life, feigned madness to avoid the Caliph's wrath. The Caliph, believing him to be insane, placed him under house arrest rather than execute him for failure. Alhazen remained there until the Caliph's death, thereby escaping punishment for his failure to accomplish a task that had been impossible from the beginning.

In 1595, a treatise on feigned diseases was published in Milan by Giambattista Silvatico. Various phases of malingering (les gueux contrefaits) are represented in the etchings and engravings of Jacques Callot (1592–1635). In his Elizabethan-era social-climbing manual, George Puttenham recommends a would-be courtier to have "sickness in his sleeve, thereby to shake off other importunities of greater consequence".

Although the concept of malingering has existed since time immemorial, the term for malingering was introduced in the 1900s due to those who would feign illness or disability to avoid military service. In 1943, US Army General George S. Patton found a soldier in a field hospital with no wounds; the soldier claimed to be suffering from battle fatigue. Believing the patient was malingering, Patton flew into a rage and physically assaulted him. The patient had malarial parasites.

Agnes was the first subject of an in-depth discussion of transgender identity in sociology, published by Harold Garfinkel in 1967. In the 1950s, Agnes feigned symptoms and lied about almost every aspect of her medical history. Garfinkel concluded that fearing she would be denied access to sexual reassignment surgery, she had avoided every aspect of her case which would have indicated gender dysphoria and hidden the fact that she had taken hormone therapy. Physicians observing her feminine appearance therefore concluded she had testicular feminization syndrome, which legitimized her request for the surgery.