Gemini 5 (officially Gemini V) was a 1965 manned spaceflight in NASA's Gemini program. It was the third manned Gemini flight, the eleventh manned American flight, and the nineteenth spaceflight of all time, including two X-15 flights above 100 kilometers (54 nmi). It was also the first time an American manned space mission held the world record for duration, set on August 26, 1965, by breaking the Soviet Union's previous record set by Vostok 5 in 1963.

On August 21, 1965 at 16:07:15 UTC, the REP was released into orbit from the Gemini 5 spacecraft.

Gemini 5 doubled the U.S space-flight record of the Gemini 4 mission to eight days, the length of time it would take to fly to the Moon, land and return. This was possible due to new fuel cells that generated enough electricity to power longer missions, a pivotal innovation for future Apollo flights, instead of the chemical batteries used on previous manned spacecraft. Cooper and Conrad were to have made a practice space rendezvous with a "pod" deployed from the spacecraft, but problems with the electrical supply forced a switch to a simpler "phantom rendezvous," whereby the Gemini craft maneuvered to a predetermined position in space. Command Pilot and Mercury veteran Gordon Cooper was the first person to fly two Earth orbital missions. He and Conrad took high-resolution photographs for the United States Department of Defense, but problems with the fuel cells and maneuvering system forced the cancellation of several other experiments. The astronauts found themselves marking time in orbit, and Conrad later lamented that he had not brought along a book. On-board medical tests, however, continued to show the feasibility of longer flights.

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