The Planetary Science Institute is a private, nonprofit 501(c)(3) corporation dedicated to Solar System exploration. It is headquartered in Tucson, AZ, where it was founded in 1972. In 2016 PSI established a second office in Lakewood, CO (near Denver). 

PSI scientists and educators are involved in numerous NASA and international missions, the study of Mars, Earth, and other planets, the Moon, asteroids, comets, interplanetary dust, impact physics, the origin of the solar system, extra-solar planet formation, dynamics, the rise of life, and other areas of research. They conduct fieldwork on all continents of the Earth to understand our planet and others. They are also actively involved around the world in science education and public outreach though school programs, children's books, popular science books, podcasts, and art.