Paul Costa Jr. (born September 16, 1942) is an American psychologist associated with the Five Factor Model.

[3] Author of over 300 academic articles, several books, he is perhaps best known for the Revised NEO Personality Inventory, or NEO PI-R, a psychological personality inventory; a 240-item measure of the Five Factor Model: Extraversion, Agreeableness, Conscientiousness, Neuroticism, and Openness to Experience.

Additionally, the test measures six subordinate dimensions (known as 'facets') of each of the "FFM" personality factors, developed together with Robert McCrae.

Work on this model has made Costa one of the most cited living psychologists,[4] with an H index of over 135.

He has argued that personality is an important influence on behavior (as opposed to situational models where individual behavior reflects no lasting individual differences), including longevity and health.