The Apollo program, also known as Project Apollo, was the third United States human spaceflight program carried out by the National Aeronautics and Space Administration (NASA), which succeeded in preparing and landing the first humans on the Moon from 1968 to 1972. It was first conceived in 1960 during President Dwight D. Eisenhower's administration as a three-person spacecraft to follow the one-person Project Mercury, which put the first Americans in space. Apollo was later dedicated to President John F. Kennedy's national goal for the 1960s of "landing a man on the Moon and returning him safely to the Earth" in an address to Congress on May 25, 1961. It was the third US human spaceflight program to fly, preceded by the two-person Project Gemini conceived in 1961 to extend spaceflight capability in support of Apollo.

Kennedy's goal was accomplished on the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module (LM) on July 20, 1969, and walked on the lunar surface, while Michael Collins remained in lunar orbit in the command and service module (CSM), and all three landed safely on Earth in the Pacific Ocean on July 24. Five subsequent Apollo missions also landed astronauts on the Moon, the last, Apollo 17, in December 1972. In these six spaceflights, twelve people walked on the Moon.

Apollo ran from 1961 to 1972, with the first crewed flight in 1968. It encountered a major setback in 1967 when an Apollo 1 cabin fire killed the entire crew during a prelaunch test. After the first successful landing, sufficient flight hardware remained for nine follow-on landings with a plan for extended lunar geological and astrophysical exploration. Budget cuts forced the cancellation of three of these. Five of the remaining six missions achieved successful landings, but the Apollo 13 landing was prevented by an oxygen tank explosion in transit to the Moon, which destroyed the service module's capability to provide electrical power, crippling the CSM's propulsion and life support systems. The crew returned to Earth safely by using the lunar module as a "lifeboat" for these functions. Apollo used the Saturn family of rockets as launch vehicles, which were also used for an Apollo Applications Program, which consisted of Skylab, a space station that supported three crewed missions in 1973–1974, and the Apollo–Soyuz Test Project, a joint United States-Soviet Union low Earth orbit mission in 1975.

Apollo set several major human spaceflight milestones. It stands alone in sending crewed missions beyond low Earth orbit. Apollo 8 was the first crewed spacecraft to orbit another celestial body, and Apollo 11 was the first crewed spacecraft to land humans on one.

Overall the Apollo program returned 842 pounds (382 kg) of lunar rocks and soil to Earth, greatly contributing to the understanding of the Moon's composition and geological history. The program laid the foundation for NASA's subsequent human spaceflight capability, and funded construction of its Johnson Space Center and Kennedy Space Center. Apollo also spurred advances in many areas of technology incidental to rocketry and human spaceflight, including avionics, telecommunications, and computers.

Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing, and then departed safely back to Earth. These three astronauts—Frank Borman, James Lovell, and William Anders—were the first humans to personally witness and photograph the far side of the Moon and an Earthrise.

Apollo 8 launched on December 21, 1968, and was the second crewed spaceflight mission flown in the United States Apollo space program after Apollo 7, which stayed in Earth orbit. Apollo 8 was the third flight and the first crewed launch of the Saturn V rocket, and was the first human spaceflight from the Kennedy Space Center, located adjacent to Cape Kennedy Air Force Station in Florida.

Originally planned as the second crewed Apollo Lunar Module and command module test, to be flown in an elliptical medium Earth orbit in early 1969, the mission profile was changed in August 1968 to a more ambitious command-module-only lunar orbital flight to be flown in December, as the lunar module was not yet ready to make its first flight. Astronaut Jim McDivitt's crew, who were training to fly the first lunar module flight in low Earth orbit, became the crew for the Apollo 9 mission, and Borman's crew were moved to the Apollo 8 mission. This left Borman's crew with two to three months' less training and preparation time than originally planned, and replaced the planned lunar module training with translunar navigation training.

Apollo 8 took 68 hours to travel the distance to the Moon. The crew orbited the Moon ten times over the course of twenty hours, during which they made a Christmas Eve television broadcast in which they read the first ten verses from the Book of Genesis. At the time, the broadcast was the most watched TV program ever. Apollo 8's successful mission paved the way for Apollo 10 and, with Apollo 11 in July 1969, the fulfillment of U.S. president John F. Kennedy's goal of landing a man on the Moon before the end of the decade. The Apollo 8 astronauts returned to Earth on December 27, 1968, when their spacecraft splashed down in the northern Pacific Ocean. The crew members were named Time magazine's "Men of the Year" for 1968 upon their return.

Apollo 1, initially designated AS-204, was the first crewed mission of the Apollo program, the American undertaking to land the first man on the Moon. It was planned to launch on February 21, 1967, as the first low Earth orbital test of the Apollo command and service module. The mission never flew; a cabin fire during a launch rehearsal test at Cape Kennedy Air Force Station Launch Complex 34 on January 27 killed all three crew members—Command Pilot Gus Grissom, Senior Pilot Ed White, and Pilot Roger B. Chaffee—and destroyed the command module (CM). The name Apollo 1, chosen by the crew, was made official by NASA in their honor after the fire.

Immediately after the fire, NASA convened an Accident Review Board to determine the cause of the fire, and both chambers of the United States Congress conducted their own committee inquiries to oversee NASA's investigation. The ignition source of the fire was determined to be electrical, and the fire spread rapidly due to combustible nylon material and the high-pressure pure oxygen cabin atmosphere. Rescue was prevented by the plug door hatch, which could not be opened against the internal pressure of the cabin. Because the rocket was unfueled, the test had not been considered hazardous, and emergency preparedness for it was poor.

During the Congressional investigation, Senator Walter Mondale publicly revealed a NASA internal document citing problems with prime Apollo contractor North American Aviation, which became known as the Phillips Report. This disclosure embarrassed NASA Administrator James E. Webb, who was unaware of the document's existence, and attracted controversy to the Apollo program. Despite congressional displeasure at NASA's lack of openness, both congressional committees ruled that the issues raised in the report had no bearing on the accident.

Crewed Apollo flights were suspended for twenty months while the command module's hazards were addressed. However, the development and uncrewed testing of the lunar module (LM) and Saturn V rocket continued. The Saturn IB launch vehicle for Apollo 1, SA-204, was used for the first LM test flight, Apollo 5. The first successful crewed Apollo mission was flown by Apollo 1's backup crew on Apollo 7 in October 1968.

Apollo 7 (October 11 – 22, 1968) was the first crewed flight in NASA's Apollo program, and saw the resumption of human spaceflight by the agency after the fire that killed the three Apollo 1 astronauts during a launch rehearsal test on January 27, 1967. The Apollo 7 crew was commanded by Walter M. Schirra, with command module pilot Donn F. Eisele and lunar module pilot R. Walter Cunningham (so designated even though Apollo 7 did not carry a Lunar Module).

The three astronauts were originally designated for the second crewed Apollo flight, and then as backups for Apollo 1. After the Apollo 1 fire, crewed flights were suspended while the cause of the accident was investigated and improvements made to the spacecraft and safety procedures, and uncrewed test flights made. Determined to prevent a repetition of the fire, the crew spent long periods monitoring the construction of their Apollo command and service modules (CSM). Training continued over much of the 21-month pause that followed the Apollo 1 disaster.

Apollo 7 was launched on October 11, 1968, from Cape Kennedy Air Force Station, Florida, and splashed down in the Atlantic Ocean eleven days later. Extensive testing of the CSM took place, and also the first live television broadcast from an American spacecraft. Despite tension between the crew and ground controllers, the mission was a complete technical success, giving NASA the confidence to send Apollo 8 into orbit around the Moon two months later. In part because of these tensions, none of the crew flew in space again, though Schirra had already announced he would retire from NASA after the flight. Apollo 7 fulfilled Apollo 1's mission of testing the CSM in low Earth orbit, and was a significant step towards NASA's goal of landing astronauts on the Moon.

Apollo 10 (May 18–26, 1969) was a human spaceflight, the fourth crewed mission in the United States Apollo program, and the second (after Apollo 8) to orbit the Moon. NASA described it as a "dress rehearsal" for the first Moon landing, and designated it an "F" mission, intended to test all spacecraft components and procedures short of actual descent and landing. While astronaut John Young remained in the Command and Service Module (CSM) orbiting the Moon, astronauts Thomas Stafford and Gene Cernan flew the Apollo Lunar Module (LM) to within 15.6 kilometers (8.4 nmi) of the lunar surface, the point at which powered descent for landing would begin on a landing mission, before rejoining Young in the CSM. After orbiting the Moon 31 times, Apollo 10 returned safely to Earth; its success enabled the first crewed landing during Apollo 11 two months later.

While NASA had considered attempting the first crewed lunar landing on Apollo 10, mission planners ultimately decided that it would be prudent to have a practice flight to hone the procedures and techniques. The crew encountered some issues during the course of the flight, namely pogo oscillations during the launch phase and a brief, uncontrolled tumble of the LM ascent stage in lunar orbit during its solo flight; however, the major mission objectives were accomplished. Stafford and Cernan observed and photographed Apollo 11's planned landing site in the Sea of Tranquility. Apollo 10 spent approximately 61 hours orbiting the Moon, for about eight of which Stafford and Cernan flew the LM apart from Young in the CSM, and about 8 days total in space. Additionally, Apollo 10 set the record for the highest speed attained by a crewed vehicle: 39,897 km/h (11.08 km/s or 24,791 mph) on May 26, 1969, during the return from the Moon.

The mission's call signs were the names of the Peanuts characters Charlie Brown for the CSM and Snoopy for the LM, who became Apollo 10's semi-official mascots. Peanuts creator Charles Schulz also drew mission-related artwork for NASA.

Apollo 15 (July 26 – August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to land on the Moon. It was the first J mission, with a longer stay on the Moon and a greater focus on science than earlier landings. Apollo 15 saw the first use of the Lunar Roving Vehicle.

The mission began on July 26 and ended on August 7, with the lunar surface exploration taking place between July 30 and August 2. Commander David Scott and Lunar Module Pilot James Irwin landed near Hadley Rille and explored the local area using the rover, allowing them to travel further from the lunar module than had been possible on previous missions. They spent 181⁄2 hours on the Moon's surface on four extravehicular activities (EVA), and collected 170 pounds (77 kg) of surface material.

At the same time, Command Module Pilot Alfred Worden orbited the Moon, operating the sensors in the scientific instrument module (SIM) bay of the service module. This suite of instruments collected data on the Moon and its environment using a panoramic camera, a gamma-ray spectrometer, a mapping camera, a laser altimeter, a mass spectrometer, and a lunar subsatellite deployed at the end of the moonwalks. The lunar module returned safely to the command module and, at the end of Apollo 15's 74th lunar orbit, the engine was fired for the journey home. During the return trip, Worden performed the first spacewalk in deep space. The Apollo 15 mission splashed down safely on August 7 despite the loss of one of its three parachutes.

The mission accomplished its goals but was marred by negative publicity the following year when it emerged that the crew had carried unauthorized postal covers to the lunar surface, some of which were sold by a West German stamp dealer. The members of the crew were reprimanded for poor judgment, and did not fly in space again. The mission also saw the collection of the Genesis Rock, thought to be part of the Moon's early crust, and Scott's use of a hammer and a feather to validate Galileo's theory that when there is no air resistance, objects fall at the same rate due to gravity regardless of their mass.

Apollo 12 (November 14 – 24, 1969) was the sixth crewed flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, by NASA from the Kennedy Space Center, Florida. Commander Charles "Pete" Conrad and Lunar Module Pilot Alan L. Bean performed just over one day and seven hours of lunar surface activity while Command Module Pilot Richard F. Gordon remained in lunar orbit.

Apollo 12 would have attempted the first lunar landing had Apollo 11 failed, but after the success of Neil Armstrong's mission, Apollo 12 was postponed by two months, and other Apollo missions also put on a more relaxed schedule. More time was allotted for geologic training in preparation for Apollo 12 than for Apollo 11, Conrad and Bean making several geology field trips in preparation for their mission. Apollo 12's spacecraft and launch vehicle were almost identical to Apollo 11's. One addition was hammocks to allow Conrad and Bean to rest more comfortably on the Moon.

Shortly after being launched on a rainy day at Kennedy Space Center, Apollo 12 was twice struck by lightning, causing instrumentation problems but little damage. Switching to the auxiliary power supply resolved the data relay problem, saving the mission. The outward journey to the Moon otherwise saw few problems. On November 19, Conrad and Bean achieved a precise landing at their expected location within walking distance of the Surveyor 3 robotic probe, which had landed on April 20, 1967. In making a pinpoint landing, they showed that NASA could plan future missions in the expectation that astronauts could land close to sites of scientific interest. Conrad and Bean carried the Apollo Lunar Surface Experiments Package, a group of nuclear-powered scientific instruments, as well as the first color television camera taken by an Apollo mission to the lunar surface, but transmission was lost after Bean accidentally pointed the camera at the Sun and its sensor was destroyed. On the second of two moonwalks, they visited Surveyor 3 and removed parts for return to Earth.

Lunar Module Intrepid lifted off from the Moon on November 20 and docked with the command module, which subsequently traveled back to Earth. The Apollo 12 mission ended on November 24 with a successful splashdown.