Launch from Cape Canaveral (KSC); landing 1600 km southwest of Honululu in the Pacific Ocean.

This mission marked the first manned lunar landing on July 20, 1969 (Neil Armstrong and Buzz Aldrin). On July 20, 1969 the lunar module (LM) Eagle separated from the command module Columbia. Michael Collins, alone aboard Columbia, inspected Eagle as it pirouetted before him to ensure the craft was not damaged. As the descent began, Neil Armstrong and Buzz Aldrin found that they were passing landmarks on the surface 4 seconds early and reported that they were "long": they would land miles west of their target point.Five minutes into the descent burn, and 6,000 feet (1,800 m) above the surface of the Moon, the LM navigation and guidance computer distracted the crew with the first of several unexpected "1202" and "1201" program alarms. Inside Mission Control Center in Houston, Texas, computer engineer Jack Garman told guidance officer Steve Bales it was safe to continue the descent and this was relayed to the crew. The program alarms indicated "executive overflows", meaning the guidance computer could not complete all of its tasks in real time and had to postpone some of them. During the mission, the cause was diagnosed as the rendezvous radar switch being in the wrong position, causing the computer to process data from both the rendezvous and landing radars at the same time. However, in 2005, software engineer Don Eyles concluded in a Guidance and Control Conference paper, that the problem was actually due to a hardware design bug that had been seen previously on testing of the first unmanned LM for Apollo 5. Having the rendezvous radar on (so that it was warmed up, in case of an emergency landing abort) should have been irrelevant to the computer, but an electrical phasing mismatch between two parts of the rendezvous radar system could cause the stationary antenna to appear to the computer as dithering back and forth between two positions, depending upon how the hardware randomly powered up. The extra spurious cycle stealing, as the rendezvous radar updated an involuntary counter, caused the computer alarms. When Neil Armstrong again looked outside, he saw that the computer's landing target was in a boulder-strewn area just north and east of a 300 metres (980 ft) diameter crater (later determined to be "West crater", named for its location in the western part of the originally planned landing ellipse). Neil Armstrong took semi-automatic control and, with Buzz Aldrin calling out altitude and velocity data, landed at 20:17 UTC on July 20, 1969 with about 25 seconds of fuel left.
Apollo 11 landed with less fuel than other missions, and the astronauts also encountered a premature low fuel warning. This was later found to have been due to greater propellant 'slosh' than expected, uncovering a fuel sensor. On subsequent missions, extra baffles were added to the tanks to prevent this. Neil Armstrong continued with the remainder of the post landing checklist, "Engine arm is off." before responding to Charles Duke with the words, "Houston, Tranquillity Base here. The Eagle has landed." Neil Armstrongs abrupt change of call sign from "Eagle" to "Tranquillity Base" caused momentary confusion at Mission Control and Charles Duke remained silent for a couple of seconds before expressing the relief of Mission Control: "Roger, Twan-- Tranquillity, we copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot." The landing area was the Sea of Tranquillity.

At 02:39 UTC on Monday July 21, 1969 (10:39pm EDT, Sunday July 20, 1969), Neil Armstrong opened the hatch, and at 02:51 UTC began his descent to the lunar surface. The Remote Control Unit controls on his chest kept him from seeing his feet. Climbing down the nine-rung ladder, Neil Armstrong pulled a D-ring to deploy the Modular Equipment Stowage Assembly (MESA) folded against Eagle's side and activate the TV camera, and at 02:56:20 UTC (10:56:20pm EDT) he set his left foot on the surface. The first landing used slow-scan television incompatible with commercial TV, so it was displayed on a special monitor and a conventional TV camera viewed this monitor, significantly reducing the quality of the picture. After describing the surface dust as "very fine-grained" and "almost like a powder", Neil Armstrong stepped off Eagle's footpad and uttered his famous line "That's one small step for [a] man, one giant leap for mankind" six and a half hours after landing. Buzz Aldrin joined him, describing the view as "Magnificent desolation." Neil Armstrong and Buzz Aldrin, who followed 13 minutes later, collected lunar rocks and other material (21.55 kg). Also a solar wind composition experiment was deployed and later recovered and they build a scientific station (EASEP), including a passive seismic experiment and a laser ranging retro reflector. The crew had a telephone call with U.S. President Richard Nixon during lunar surface staying and they erected the U.S. flag.

The total lunar surface stay time was 21h 36m. At 17:54 UTC, they lifted off in Eagle's ascent stage, carrying 21.5 kilograms of lunar samples with them, to rejoin CMP Michael Collins aboard Columbia in lunar orbit. During the launch Buzz Aldrin looked up in time to see the exhaust from the ascent module's engine knock over the American flag they had planted. The two spacecrafts performed asuccessful docking of LM Eagle with CSM Columbia (with Michael Collins on board, who had little to do, while Neil Armstrong and Buzz Aldrin landed on the moon).

The recovery ship was the USS Hornet. The astronauts were carried by helicopter to the Hornet where they entered a mobile quarantine facility to begin a 17 day-period of observation under strict quarantine conditions.