Launch Complex 39A (LC-39A) is the first of Launch Complex 39's three launch sub-complexes, located at NASA's Kennedy Space Center in Merritt Island, Florida. The main launch pad, along with Launch Complex 39B, was built in the 1960s to accommodate the Saturn V launch vehicle, and has been used to support NASA crewed space flight missions, including the historic Apollo 11 moon landing and the Space Shuttle. Since 2014 the site has been leased by SpaceX and supports launches of the Falcon 9 and Falcon Heavy rockets. As of August 2025, there are plans to add two landing zones for Falcon 9 and Falcon Heavy rockets to conduct to "Return-to-launch-site" landings. Other plans include adding an "Orbital Launch Platform" adjacent to the existing Starship launch tower, a catch tower, and other infrastructure to permit Starship launches.

In 1961, U.S. President Kennedy proposed to the U.S. Congress the goal of landing a man on the Moon by the end of the decade. Congressional approval led to the launch of the Apollo program, which required a massive expansion of NASA operations, including an expansion of launch operations from the Cape to adjacent Merritt Island to the north and west.

First named Launch Complex 39C, Launch Complex 39A was designed to handle launches of the Saturn V rocket, the largest and most powerful launch vehicle, which would propel the Apollo spacecraft to the Moon. The first launch from Launch Complex 39A occurred in 1967 with the first Saturn V launch, which carried the uncrewed Apollo 4 spacecraft. The second uncrewed launch, Apollo 6, also used Pad 39A. With the exception of Apollo 10, which used Pad 39B (due to the "all-up" testing resulting in a 2-month turnaround period), all crewed Apollo-Saturn V launches, commencing with Apollo 8, used Pad 39A.

Launch Complex 39A was used for the uncrewed launch of the Skylab space station on May 14, 1973. This used a modified Saturn V originally built for the cancelled Apollo 18 mission. The subsequent Skylab crewed missions launched from Launch Complex 39B using Saturn IB launch vehicles.

With the advent of the Space Shuttle program in the early 1980s, the original structure of the launch pads was remodeled for the needs of the Space Shuttle. The first usage of Pad 39A for the Space Shuttle came in 1979, when Enterprise was used to check the facilities prior to the first operational launch. Since then, Pad 39A hosted all Space Shuttle launches until January 1986, when Space Shuttle Challenger would become the first to launch from pad 39B during the ill-fated STS-51-L mission.

During the launch of Discovery on STS-124 on May 31, 2008, the pad at LC-39A suffered extensive damage, in particular to the concrete trench used to deflect the SRBs' flames. The subsequent investigation found that the damage was the result of carbonation of epoxy and corrosion of steel anchors that held the refractory bricks in the trench in place. The damage had been exacerbated by the fact that hydrochloric acid is an exhaust by-product of the solid rocket boosters.

Just as for the first 24 shuttle flights, LC-39A supported the final shuttle flights, starting with STS-117 in June 2007 and ending with the retirement of the Shuttle fleet in July 2011. In total, Pad 39A hosted 94 launches from 1967 to 2011, including 12 Saturn V rockets and 82 space shuttles. Prior to the SpaceX lease agreement, the pad remained as it was when Atlantis launched on the final shuttle mission on July 8, 2011, complete with a mobile launcher platform. The pad was originally going to be modified for the Ares V rocket for the Constellation program in the mid 2010s, looking identical to LC-39B with the three lightning towers. The Ares I was planned to launch on the adjacent 39B but in 2010, the Constellation program was cancelled.

Talks for use of the pad were underway between NASA and Space Florida—the State of Florida's economic development agency—as early as 2011, but no deal materialized by 2012, and NASA then pursued other options for removing the pad from the federal government inventory.