SIRTF, -the Space Infrared Telescope Facility, is to be launched by NASA early in 2003. SIRTF will be an observatory for infrared astronomy from space with an 85cm aperture telescope operating at 5.5K and a 2.5-to-5 year cryogenic lifetime. SIRTF's three instruments with state of the art detector arrays will provide imaging, photometry, and spectroscopy over the 3-180um wavelength range. SIRTF will provide major advances for the study of astrophysical problems from the solar system to the edge of the Universe. SIRTF will complete NASA's family of Great Observatories and serve as a cornerstone of the Origins program. Over 75% of the observing time will be awarded to the general scientific community through the usual proposal and peer review cycle. SIRTF will demonstrate major advances in technology areas critical to future infrared missions. These include lightweight cryogenic optics, sensitive detector arrays, and a high performance thermal system, combining radiative and cryogenic cooling, which allows the telescope to be launched warm and to cool in space. These thermal advances are enabled by the use of an Earth-trailing solar orbit which carries SIRTF to a distance of ~0.6 AU from Earth in 5 years. This paper will provide an overview of the SIRTF mission, -telescope, cryostat, instruments, spacecraft, orbit, and operations - in preparation for an accompanying set of detailed technical presentations.