Gemini 3 was the first manned mission of Project Gemini, which aimed to launch a series of two-man spacecraft to test long-duration missions, rendezvous and docking between two space vehicles, and EVA or "spacewalking." Command pilot Virgil I. "Gus" Grissom and pilot John Young were launched from Cape Kennedy on March 23, 1965, atop a Titan II launch vehicle. Because Grissom's Mercury spacecraft, Liberty Bell 7, had sunk at the end of his 1961 suborbital mission, he unofficially named Gemini 3 for the "Unsinkable Molly Brown" of Broadway musical fame. The crew successfully completed the planned 3-orbit mission in just under 5 hours. Their primary objectives were to test the basic systems of the Gemini spacecraft and make the first orbit-changing maneuvers in space.

After the mission, the Gemini 3 capsule was used for testing in the military Manned Orbiting Laboratory program before being given to the Smithsonian in 1970.