INFJ (introversion, intuition, feeling, judging) is an initialism used in the publications of the Myers–Briggs Type Indicator (MBTI) to refer to one of the sixteen personality types. The MBTI assessment was developed from the work of prominent psychiatrist Carl Jung in his book Psychological Types. Jung proposed a psychological typology based on the theories of cognitive functions that he developed through his clinical observations.
From Jung's work, others developed psychological typologies. Jungian personality assessments include the MBTI instrument, developed by Isabel Briggs Myers and Katharine Cook Briggs, and the Keirsey Temperament Sorter, developed by David Keirsey. Keirsey referred to the INFJs as Counselors, one of the four types belonging to the temperament he called the Idealists. INFJs are the rarest type, and make up about 1–3% of the general populace or less.