The Planetary Science Institute (PSI) is a 501(c)(3) non-profit research institute based in Tucson, Arizona, focusing on planetary science. As of 2018, its director is Dr. Mark V. Sykes. PSI, along with Space Science Institute (SSI) Southwest Research Institute (SwRI), and Eureka Scientific, were listed as 501(c)(3) organizations in the US in a special report by Nature in 2007, which facilitate federal grant applications of non-tenure-track astronomers.