Space Shuttle Discovery (Orbiter Vehicle Designation: OV-103) is one of the three currently operational spacecraft in the Space Shuttle fleet of NASA. When first flown in 1984, Discovery became the third operational orbiter and is now the oldest orbiter in service. Discovery has performed both research and International Space Station (ISS) assembly missions. Discovery was also notable for being named after one of the two ships that were used by British explorer James Cook in the 1770's, during voyages in the South Pacific that led to the discovery of the Hawaiian Islands. Discovery was the shuttle that launched the Hubble Space Telescope. The second and third Hubble service missions were also conducted by Discovery. It has also launched the Ulysses probe and three TDRS satellites.

Discovery has been chosen twice as the return to flight orbiter, first in 1988 as the return to flight orbiter after the 1986 Challenger disaster, and then for the twin return to flight missions in July 2005 and July 2006 after the 2003 Columbia disaster. Discovery also carried Project Mercury astronaut John Glenn, who was 77 at the time, back into space during STS-95 on October 29, 1998, making him the oldest human being to venture into space.

Discovery is currently in bay 3 of the Orbiter Processing Facility, having concluded a 15-day mission to the International Space Station on November 7, 2007. After the residual cryogenic reactants are offloaded the payload bay doors will be opened and detailed post-flight inspections will begin.

According to the current schedule, Space Shuttle Discovery will be decommissioned in 2010. If the Contingency Logistic Flight STS-133 by Endeavour is not flown, Discovery will be the last space shuttle to fly on mission STS-132. NASA expects to launch the Orion Crew Exploration Vehicle on the new Ares I rocket by 2014.