The Imaging X-ray Polarimetry Explorer (IXPE) will exploit the polarization state of light from astrophysical sources to provide insight into our understanding of X-ray production in objects such as neutron stars and pulsar wind nebulae, as well as stellar and supermassive black holes. IXPE will improve sensitivity over OSO-8, the only previous X-ray polarimeter, by two orders of magnitude in required exposure time. IXPE also will introduce the capability for X-ray polarimetric imaging, uniquely enabling the measurement of X-ray polarization with scientifically meaningful spatial, spectral, and temporal resolution, to address NASA's Science Mission Directorate's science goal "to probe the origin and destiny of our universe, including the nature of black holes, dark energy, dark matter, and gravity."