An autonomous sensory meridian response (ASMR) is a tingling sensation that usually begins on the scalp and moves down the back of the neck and upper spine. A pleasant form of paresthesia, it has been compared with auditory-tactile synesthesia and may overlap with frisson. ASMR is a subjective experience of "low-grade euphoria" characterized by "a combination of positive feelings and a distinct static-like tingling sensation on the skin". It is most commonly triggered by specific auditory stimuli, and less commonly by intentional attention control and visual stimuli.

The term can also refer to media (usually audiovisual) meant to evoke this phenomenon, with the sensation itself being informally referred to as "tingles".

Although many colloquial and formal terms used and proposed between 2007 and 2010 included reference to orgasm, a significant majority objected to its use among those active in online discussions. Many differentiate between the euphoric, relaxing nature of ASMR and sexual arousal. However, the argument for sexual arousal persists, and some proponents have published videos categorized as "ASMRotica" (ASMR erotica), which are deliberately designed to be sexually stimulating.

Early proponents of ASMR concluded that the phenomenon was generally unrelated to sexual arousal. In 2010, Jennifer Allen, a participant in an online forum, proposed that the phenomenon be named "autonomous sensory meridian response". Allen chose the words intending or assuming them to have the following specific meanings:

Allen confirmed in a 2016 interview that she purposely selected these terms because they were more objective, comfortable, and clinical, rather than alternative terms for the sensation. In that interview, Allen explained she selected the word meridian to replace the word orgasm and said she had found a dictionary that defined meridian as "a point or period of highest development, greatest prosperity, or the like".

The subjective experience, sensation, and perceptual phenomenon of ASMR is described by some of those susceptible to it as "akin to a mild electrical current ... or the carbonated bubbles in a glass of champagne". The tingling sensation on one's skin in general, called paresthesia, is referred to by ASMR enthusiasts as "tingles" when experienced along the scalp, neck, and back. It has been described as "a static tingling sensation originating from the back of the head, then propagating to the neck, shoulder, arm, spine, and legs, which makes people feel relaxed and alert".

Though little scientific research has been conducted into potential neurobiological correlations to the perceptual phenomenon, with a consequent dearth of data with which to explain its physical nature, personal commentary from forums, blog posts, and video comments have been analyzed to describe the phenomenon. Analysis of this anecdotal evidence support the original consensus that ASMR is euphoric but non-sexual, and it has divided those who experience ASMR into two broad categories of subjects. One category depends upon external triggers to experience the localized sensation and its associated feelings, which typically originate in the head, often reaching down the neck and sometimes the upper back. The other category can intentionally augment the sensation and feelings without dependence upon external stimuli through attentional control, in a manner that some subjects likened to their experience of meditation.

ASMR is usually precipitated by stimuli referred to as "triggers". ASMR triggers, which are most commonly auditory and visual, may be encountered through the interpersonal interactions of daily life. Additionally, ASMR is often triggered by exposure to specific audio and video. Such media may be specially made with the specific purpose of triggering ASMR, or created for other purposes and later discovered to be effective as a trigger.