The Advanced X-ray Astrophysics Facility (AXAF) is to be a free-flying national x-ray observatory that is Shuttle-launched (in mid-1988), maintainable on-orbit, and retrievable. The design lifetime is > 10 years. The AXAF is conceived as an x-ray telescope with 6 nested Wolter type I mirrors (maximum aperture of 1.2 m), a focal length of 10 m, and interchangeable and replaceable focal plane instruments. The optics will provide 0.5 arcsecond imagery over a several arcminute field and somewhat reduced resolution over 1 degree in the x-ray band from 0.1 to 8 keV. The performance requirements and design of the facility will be discussed and comparisons made with an existing x-ray observatory. The scientific objectives of the AXAF will also be discussed briefly.