A mission patch is a cloth reproduction of a spaceflight mission emblem worn by astronauts and other personnel affiliated with that mission. It is usually executed as an embroidered patch. The term space patch is mostly applied to an emblem designed for a crewed space mission. Traditionally, the patch is worn on the space suit that astronauts and cosmonauts wear when launched into space. Mission patches have been adopted by the crew and personnel of many other space ventures, public and private.

The idea of creating distinctive patches for military missions or units began during the US Civil War, when the Army of the Potomac introduced special insignias to distinguish its corps and divisions. This practice faded after General Robert E. Lee surrendered at Appomattox and the army disbanded. However, the tradition was brought back with the onset of World War I and has since become widespread across all branches of the military, used in both wartime and peacetime.

The first space patch was flown by Soviet cosmonaut Valentina Tereshkova on the Vostok 6 mission in 1963; however, that was hidden from public view by the bright orange coverall that was part of the space suit at the time. At the start of the human spaceflight space age, as a rule, astronauts were pilots from a military background. These pilots took the tradition of military shoulder patches with them; most US space missions have had dedicated designs, and since the mid-1980s most Soviet/Russian flights also featured space patches. Mission patches were first sported by NASA astronauts in 1965. The idea was first introduced to NASA by Air Force pilot (and astronaut) Gordon Cooper.

Following the loss of the Apollo 1 crew in a devastating fire, embroidered patches were restricted from crew clothing. Instead, astronauts in flight wore mission patches of fire-resistant Beta cloth onto which designs were silkscreened. (Embroidered patches were still produced for ground side wear, non-flight personnel, sale to collectors and to be flown in space as souvenirs.)

The Vostok-6 patch was the only one of that program. The first spacewalker, Alexei Leonov wore a general patch on his EVA representing a rocket taking off Earth, which was also used on subsequent flights. As part of the Interkosmos program, the crewed flights to the Salyut and Mir space stations between 1978 and 1988 featured mission logos. After that, some international flights had a patch, but only from 1994 onward did every Russian crewed launch feature a space patch. At that time, the design and production of the patches was done on the initiative of the crew; the designs were not sanctioned by the Russian space agency (Glavkosmos/RKA/Roscosmos). On a few confusing occasions, that lead to two 'crew-approved' patches existing for a single mission. The first agency-approved Russian space patch was the one for Soyuz TMA-13. However, Roscosmos was very late in announcing the design, by which time the crew had already produced their own version; the official design was not worn on the crew's suits. Since Soyuz TMA-14 in 2009, all launches feature 'official' patches.

Early crewed NASA missions lacked patches; instead, the astronauts gave their spacecraft names. (Alan Shepard's capsule for Mercury 3 was named Freedom 7, for instance.) When Gus Grissom proposed to name his Gemini 3 capsule Molly Brown—a reference to The Unsinkable Molly Brown, referring in turn to Grissom's Mercury 4 capsule which sank in the ocean shortly after splashdown – NASA officials were nonplussed and they abolished the practice of naming capsules.

This prompted astronaut Gordon Cooper to propose and develop a mission patch for his and Pete Conrad's 1965 Gemini 5 flight: an embroidered cloth patch sporting the names of the two crew members, a covered wagon, and the slogan "8 Days or Bust" which referred to the expected mission duration. NASA administrator James E. Webb approved the design, but insisted on the removal of the slogan from the official version of the patch. The so-called Cooper patch was worn on the right breast of the astronauts' uniforms below their nameplates and opposite the NASA emblems worn on the left.

Since Gemini 5, patches have been created for all NASA crewed missions and many uncrewed expeditions. Patches are now created by professional graphic designers, but the design is still directed by each astronaut crew. They are designed and manufactured by A-B Emblem in North Carolina.