Autosuggestion is the process by which an individual trains their subconscious mind to believe something. This is accomplished through self-hypnosis methods or repetitive, constant self-affirmations, and may be seen as a form of self-induced brainwashing. The acceptance of autosuggestions may be quickened through mental visualization of that which the individual would like to believe. Its successfulness is typically correlated to the consistency of its use and the length of time over which its used.

Autosuggestion is most commonly accomplished by bombarding the mind with repetitive thoughts until they are self-accepted by ones mind, whether they are negative or positive thoughts. Practitioners hope to transmute their thoughts into beliefs or actualities. It can be both a conscious process or unintentional process, though almost exclusively thought of as a deliberate tool. Visualizing the manifestations of a belief, verbally affirming one, and thinking one using one's "internal voice" are typical means of influencing one's mind via repetitive autosuggestion.

Applications of autosuggestion are intended to change the way one believes, perceives, or thinks, acts, or is composed physically or physiologically. An example may be an individual reading nightly aloud a statement he or she has constructed that describes how he or she would like to be, then repeating the statement in his or her mind until he or she falls asleep. People have attributed such a nightly routine or similar employment of autosuggestion with changes like increased confidence, the conquering of life-long fears, heightened mental faculties (i.e. ability to calculate mathematics or read at a quicker rate), diseases or infections being eradicated from one's body, and even improved eyesight and growing taller.

The same effect that autosuggestion achieves may be seen also in individuals not consciously trying to program themselves through autosuggestion. The dominant thoughts of a person which occupy their conscious mind, if constantly present over an extended period of time, may be training that person's subconscious mind to believe what that individual cognitively is thinking. In this way, fixations and obsessions may also been seen similar to autosuggestions.

Autosuggestion is differentiated from brainwashing or hypnosis in that it is a self-induced process only. An idea may be introduced by another, but autosuggestion is the processes wherein one's own mind redefines its beliefs itself.