The Myers-Briggs Type Indicator (MBTI) assessment is a psychometric questionnaire designed to measure psychological preferences in how people perceive the world and make decisions. These preferences were extrapolated from the typological theories originated by Carl Gustav Jung, as published in his 1921 book Psychological Types (English edition, 1923). The original developers of the personality inventory were Katharine Cook Briggs and her daughter, Isabel Briggs Myers. They began creating the indicator during World War II, believing that a knowledge of personality preferences would help women who were entering the industrial workforce for the first time to identify the sort of war-time jobs where they would be "most comfortable and effective." The initial questionnaire grew into the Myers-Briggs Type Indicator, which was first published in 1962. The MBTI focuses on normal populations and emphasizes the value of naturally occurring differences.

The MBTI instrument is called "the best-known and most trusted personality assessment tool available today" by its publisher, CPP (formerly Consulting Psychologists Press). CPP further calls the MBTI tool "the world’s most widely used personality assessment", with as many as two million assessments administered annually. Some academic psychologists have criticized the MBTI instrument, claiming that it "lacks convincing validity data". Proponents of the test, however, cite reports of individual behavior and have also found that the indicator meets or exceeds the reliability of other psychological instruments. For most adults (75–90%), though not for children, the MBTI is reported to give the same result for 3–4 preferences when the test is administered to the same person more than once (although the period between measurements is not stated). Some studies have found strong support for construct validity, internal consistency, and test-retest reliability, although variation was observed.

The definitive published source of reference for the Myers-Briggs Type Indicator is The Manual produced by CPP, from which much of the information in this article is drawn, along with training materials from CPP and their European training partners, Oxford Psychologists Press. Also, a related model, with an original test, is published in David Keirsey's books Please Understand Me and Please Understand Me II.

The registered trademark rights to the terms Myers-Briggs Type Indicator and MBTI have been assigned from the publisher of the test, CPP, Inc., to the Myers-Briggs Type Indicator Trust.