Apollo 11 (AS-506) was the first mission in which humans walked on the Lunar surface and returned to Earth: On 20 July 1969, two astronauts (Apollo 11 Commander Neil A. Armstrong and "Eagle" Lunar Module (LM) pilot Edwin E. "Buzz" Aldrin Jr.) landed in Mare Tranquilitatis (the Sea of Tranquility) on the Moon in the LM while the "Columbia" Command and Service Module (CSM), with CM pilot Michael Collins, continued in Lunar orbit. During their stay on the Moon, the astronauts set up scientific experiments, took photographs, and collected Lunar samples. The LM took off from the Moon on 21 July and the astronauts returned to Earth on 24 July.

Apollo 11, the fifth manned Apollo mission, was launched into Earth orbit on 16 July 1969 from pad 39A of the Kennedy Space Center, Florida, on a Saturn V. After 1.5 Earth orbits, the S-IVB stage was re-ignited at 16:16:16 UT for the 5 minute 48 second translunar injection burn, putting the spacecraft on course for the Moon. The CSM separated from the S-IVB stage containing the LM 33 minutes later, turned around and docked with the LM at 16:56:03 UT. About an hour and 15 minutes later, the S-IVB stage was injected into heliocentric orbit. On 17 July, a three second mid-course correction burn of the main engine was performed. During the translunar coast, at 4:40 pm EDT on 18 July, the crew began a 96 minute color television transmission of the CSM and LM interiors, CSM exterior, the Earth, probe and drogue removal, spacecraft tunnel hatch opening, food preparation, and LM housekeeping. Lunar orbit insertion was achieved on 19 July at 17:21:50 UT by a retrograde firing of the main engine for 357.5 seconds while the spacecraft was behind the Moon and out of contact with Earth, and a 17 second burn later circularized the orbit. During the second Lunar orbit, a live color telecast of the Lunar surface was made. At 13:50 UT on 20 July, Armstrong and Aldrin entered the LM for the final systems checkout. At 18:11:53, the LM and CSM separated, and after a visual inspection by Collins, the LM descent engine was fired for 30 seconds at 19:08 UT, putting the craft into a descent orbit with a closest approach 14.5 km above the Moon's surface. At 20:05, the LM descent engine was fired for 756.3 seconds, and the final descent to the Lunar surface began.

The first Apollo landing site, in the southern Sea of Tranquility about 20 km (12 mi) southwest of the crater Sabine D, was selected in part because it had been characterized as relatively flat and smooth by the automated Ranger 8 and Surveyor 5 landers, as well as by Lunar Orbiter mapping spacecraft, and therefore unlikely to present major landing or extra-vehicular activity (EVA) challenges.

Armstrong and Aldrin found they were "running long" - Eagle was 4 seconds further along its descent trajectory than planned, and would land miles west of the intended site. The LM navigation and guidance computer reported several "program alarms" as it guided the LM's descent which tore the crew's attention from the scene outside as the descent proceeded. A young controller named Steve Bales at NASA's Mission Control Center in Houston, Texas, was able to tell the flight director it was safe to continue the descent in spite of the alarms (for which he later received the Medal of Freedom). Once they were able to return their attention to the view outside, the astronauts saw that their computer was guiding them toward a landing site full of large rocks scattered around a large crater. Armstrong took manual control of the Lunar module, and guided it to a landing with less than 30 seconds worth of fuel left. The program alarms were "executive overflows" indicating the computer could not finish its work in the time allotted. The cause was later determined to be the LM rendezvous radar was left on during the descent, causing the computer to spend unplanned time servicing the unused radar.

The LM landed at 20:17:40 UT (4:17:40 pm EDT) in Mare Tranquilitatis (the Sea of Tranquility), with Armstrong reporting, "Houston, Tranquility Base here - the Eagle has landed." Armstrong stepped onto the Lunar surface at 02:56:15 UT on 21 July (10:56:15 pm July 20 EDT) stating, "That's one small step for man, one giant leap for mankind." Aldrin followed him onto the Lunar surface 19 minutes later. The astronauts unveiled a plaque mounted on a strut of the LM and read to a worldwide TV audience, "Here men from the planet Earth first set foot on the Moon July 1969, A.D. We came in peace for all mankind." After raising the American flag and talking to President Nixon by radiotelephone, the astronauts deployed the Early Apollo Scientific Experiment Package (EASEP) and other instruments, took photographs, and collected 21.7 kg of Lunar rock and soil, traversing a total distance of about 250 meters. Despite some technical and weather difficulties, ghostly black and white images of the entire first Lunar EVA were received, primarily through the radio telescope station at the Parkes Observatory in Australia, and were immediately broadcast live to at least 600 million people on Earth. The EVA ended at 5:11:13 UT when Armstrong and Aldrin returned to the LM and closed the hatch.

The LM lifted off from the Moon at 17:54:01 UT on 21 July after 21 hours, 36 minutes on the Lunar surface. After docking with the CSM at 21:34:00 UT, the crew, with the Lunar samples and film, transferred to the CSM. The LM was jettisoned into Lunar orbit at 00:01:01 UT on 22 July. The crew then rested and prepared for the return trip to Earth. Transearth injection began at 04:54:42 UT on 22 July with a 2.5 minute firing of the CSM main engine. Following a midcourse correction at 21:01 UT, an 18 minute color television transmission was made, in which the astronauts demonstrated the weightlessness of food and water, and showed shots of the Earth and Moon. The CM separated from the SM at 16:21:13 UT on 24 July as the spacecraft neared Earth on its return. Apollo 11 splashed down in the Pacific Ocean on 24 July 1969 at 16:50:35 UT (12:50:35 pm EDT) after a mission elapsed time of 195 hours, 18 minutes, 35 seconds. Splashdown took place at 13 deg 19 min N, 169 deg 9 min W, 400 miles SSW of Wake Island and 24 km (15 mi) from the recovery ship USS Hornet. Following decontamination procedures at the splashdown point, the astronauts were carried by helicopter to the Hornet where they entered a mobile quarantine facility to begin a period of observation under strict quarantine conditions. The CM was also recovered and removed to the quarantine facility. Sample containers and film were flown to Houston.

All primary mission objectives and all detailed test objectives of Apollo 11 were met, and all crew members remained in good health. The performance of the spacecraft was excellent throughout the mission. The primary mission goal of landing astronauts on the Moon and returning them to Earth was achieved. Armstrong was a civilian on his second spaceflight (he'd previously flown on Gemini 8), Aldrin was a USAF Colonel on his second spaceflight (Gemini 12), Collins was a USAF Lt. Colonel also on his second flight (Gemini 10). The backup crew for the mission was Jim Lovell, Fred Haise, and William Anders. The Apollo 11 Command Module is on display at the National Air and Space Museum in Washington, DC.

Apollo 11's Moon landing is the basis of selecting 20 July - Moon Day - as one of the L5 National Holidays.

The Apollo program included a large number of uncrewed test missions and 12 crewed missions: three Earth orbiting missions (Apollo 7, 9 and Apollo-Soyuz), two Lunar orbiting missions (Apollo 8 and 10), a Lunar swingby (Apollo 13), and six Moon landing missions (Apollo 11, 12, 14, 15, 16, and 17). Two astronauts from each of the six landing missions walked on the Moon (Neil Armstrong, Edwin Aldrin, Charles Conrad, Alan Bean, Alan Shepard, Edgar Mitchell, David Scott, James Irwin, John Young, Charles Duke, Gene Cernan, and Harrison Schmitt), the only humans to date (2022) to have set foot on another planetary body beyond Earth.

https://nssdc.gsfc.nasa.gov/planetary/lunar/apollo11info.html