Alan Shepard in the context of "Human spaceflight"

Project Mercury was the first human spaceflight program of the United States, running from 1958 through 1963. An early highlight of the Space Race, its goal was to put a man into Earth orbit and return him safely, ideally before the Soviet Union. Taken over from the US Air Force by the newly created civilian space agency NASA, it conducted 20 uncrewed developmental flights (some using animals), and six successful flights by astronauts. The program, which took its name from Roman mythology, cost $2.76 billion (adjusted for inflation). The astronauts were collectively known as the "Mercury Seven", and each spacecraft was given a name ending with a "7" by its pilot.

The Space Race began with the 1957 launch of the Soviet satellite Sputnik 1. This came as a shock to the American public, and led to the creation of NASA to expedite existing US space exploration efforts, and place most of them under civilian control. After the successful launch of the Explorer 1 satellite in 1958, crewed spaceflight became the next goal. The Soviet Union put the first human, cosmonaut Yuri Gagarin, into a single orbit aboard Vostok 1 on April 12, 1961. Shortly after this, on May 5, the US launched its first astronaut, Alan Shepard, on a suborbital flight. Soviet Gherman Titov followed with a day-long orbital flight in August 1961. The US reached its orbital goal on February 20, 1962, when John Glenn made three orbits around the Earth. When Mercury ended in May 1963, both nations had sent six people into space, but the Soviets led the US in total time spent in space.

The Mercury Seven were the group of seven astronauts selected to fly spacecraft for Project Mercury. They are also referred to as the Original Seven and Astronaut Group 1. Their names were publicly announced by NASA on April 9, 1959: Scott Carpenter, Gordon Cooper, John Glenn, Gus Grissom, Wally Schirra, Alan Shepard, and Deke Slayton. The Mercury Seven created a new profession in the United States, and established the image of the American astronaut for decades to come.

All of the Mercury Seven eventually flew in space. They piloted the six spaceflights of the Mercury program that had an astronaut on board from May 1961 to May 1963, and members of the group flew on all of the NASA human spaceflight programs of the 20th century – Mercury, Gemini, Apollo, and the Space Shuttle.

Gherman Stepanovich Titov (Russian: Герман Степанович Титов; 11 September 1935 – 20 September 2000) was a Soviet and Russian cosmonaut who, on 6 August 1961, became the second human to orbit the Earth, aboard Vostok 2, preceded by Yuri Gagarin on Vostok 1. He was the fourth person in space, counting suborbital voyages of US astronauts Alan Shepard and Gus Grissom. A month short of 26 years old at launch, he is the youngest professional astronaut and was the youngest person to fly in space until 2021 when Oliver Daemen flew on Blue Origin NS-16 at the age of 18. Since Daemen flew a suborbital mission, Titov remains the youngest person to fly in Earth orbit.

Titov's flight finally proved that humans could live and work in space. He was the first person to orbit the Earth multiple times (a total of 17), the first to pilot a spaceship and to spend more than a day in space. He was also the first to sleep in orbit and to suffer from space sickness (becoming the first person to vomit in space).

Mercury-Redstone 3, or Freedom 7, was the first United States human spaceflight, on May 5, 1961, piloted by astronaut Alan Shepard. It was the first crewed flight of Project Mercury. The project had the ultimate objective of putting an astronaut into orbit around the Earth and returning him safely. Shepard's mission was a 15-minute suborbital flight with the primary objective of demonstrating his ability to withstand the high g-forces of launch and atmospheric re-entry.

Shepard named his space capsule Freedom 7, setting a precedent for the remaining six Mercury astronauts naming their spacecraft and the format of their names, the number 7 later included in all the crewed Mercury spacecraft names not to honor NASA's first group of seven astronauts but it stood for the McDonnell Model #7 space capsule used in the Mercury Program. His spacecraft reached an altitude of 101.2 nautical miles (116.5 statute miles, 187.5 km) and traveled a downrange distance of 263.1 nautical miles (302.8 statute miles, 487.3 km). It was the fourth Mercury flight launched with the Mercury-Redstone Launch Vehicle, from Cape Canaveral, Florida, close to the Atlantic Ocean.

Mercury-Atlas 10 (MA-10) was a cancelled early crewed space mission, which would have been the last flight in NASA's Mercury program. It was planned as a three-day extended mission, to launch in late 1963; the spacecraft, Freedom 7-II, would have been flown by Alan Shepard, a veteran of the suborbital Mercury-Redstone 3 mission in 1961. However, it was cancelled after the success of the one-day Mercury-Atlas 9 mission in May 1963, to allow NASA to focus its efforts on the more advanced two-man Gemini program.