John George Geier, III (Flint, Michigan; January 24, 1934 – September 26, 2009) was an American psychologist who worked extensively on the DISC assessment systems, which improve work/life performance. Dr. Geier had a 40-year career in the assessment process and was known as a pioneer and founder of personnel selection, training and research, and a leader of human assessment. During his career, he developed numerous assessment tools, including the DiSC Personal Profile System, and the Personality Factor Profile, used for more than 50 million people around the world and translated to more than 30 different languages.