The NSF Astronomy and Astrophysics Postdoctoral Fellowships provide an opportunity for highly qualified, recent doctoral scientists to carry out an integrated program of independent research and education. Fellows may engage in observational, instrumental, theoretical, laboratory or archival data research in any area of astronomy or astrophysics, in combination with a coherent educational plan for the duration of the fellowship. The program supports researchers for a period of up to three years with fellowships that may be taken to eligible host institutions of their choice. The program is intended to recognize early-career investigators of significant potential and to provide them with experience in research and education that will establish them in positions of distinction and leadership in the scientific community. • The fellowship candidate must identify one or more scientific mentor(s) and host institution(s) at the time of proposal submission. • Prospective Fellows may propose to hold the fellowship at U.S. institutions of higher education, NSF-funded centers, facilities, or institutes, U.S. non-profit organizations with research and educational missions, or International sites that are operated by U.S. organizations eligible for NSF funding. • National centers, facilities, sites, or institutes funded by other federal agencies, such as NASA or the U.S. Department of Energy, are ineligible as host institutions for the NSF AAPF Program.