An auditory hallucination, or paracusia, is a form of hallucination that involves perceiving sounds without auditory stimulus. While experiencing an auditory hallucination, the affected person hears a sound or sounds that did not come from the natural environment.

A common form of auditory hallucination involves hearing one or more voices without a speaker present, known as an auditory verbal hallucination. This may be associated with psychotic disorders, most notably schizophrenia, and this phenomenon is often used to diagnose these conditions. However, individuals without any mental disorders may hear voices, including those under the influence of mind-altering substances, such as cannabis, cocaine, amphetamines, and PCP.

There are three main categories into which the hearing of talking voices often fall: a person hearing a voice speak one's thoughts, a person hearing one or more voices arguing, or a person hearing a voice narrating their own actions. These three categories do not account for all types of auditory hallucinations.

Hallucinations of music also occur. In these, people more often hear snippets of songs that they know, or the music they hear may be original. They may occur in mentally sound people and with no known cause. Other types of auditory hallucinations include exploding head syndrome and musical ear syndrome. In the latter, people will hear music playing in their mind, usually songs they are familiar with. These hallucinations can be caused by: lesions on the brain stem (often resulting from a stroke), sleep disorders such as narcolepsy, tumors, encephalitis, or abscesses. This should be distinguished from the commonly experienced phenomenon of earworms, memorable music that persists in one's mind. Reports have also mentioned that it is also possible to get musical hallucinations from listening to music for long periods of time. Other causes include hearing loss and epileptic activity.

In the past, the cause of auditory hallucinations was attributed to cognitive suppression by way of executive function failure of the frontoparietal sulcus. Newer research has found that they coincide with the left superior temporal gyrus, suggesting that they are better attributed to speech misrepresentations. It is assumed through research that the neural pathways involved in normal speech perception and production, which are lateralized to the left temporal lobe, also underlie auditory hallucinations. Auditory hallucinations correspond with spontaneous neural activity of the left temporal lobe, and the subsequent primary auditory cortex. The perception of auditory hallucinations corresponds to the experience of actual external hearing, despite the absence of any sound itself.

In 2015 a small survey reported voice hearing in persons with a wide variety of DSM-5 diagnoses, including:

However, numerous persons surveyed reported no diagnosis. In his 2012 book Hallucinations, neurologist Oliver Sacks describes experiences of voice hearing both from patients with a wide variety of medical conditions and from himself. Genetic correlations have been identified with auditory hallucinations, but most work with non-psychotic causes of auditory hallucinations is still ongoing.

In people with psychosis, the premier cause of auditory hallucinations is schizophrenia, and these are known as auditory verbal hallucinations (AVHs). In schizophrenia, people show a consistent increase in activity of the thalamic and striatal subcortical nuclei, hypothalamus, and paralimbic regions; confirmed by PET and fMRI scans. Other research shows an enlargement of temporal white matter, frontal gray matter, and temporal gray matter volumes (those areas crucial to both inner and outer speech) when compared to (healthy) control groups. This implies that functional and structural abnormalities in the brain, both of which may have a genetic component, can induce auditory hallucinations.