Launch Complex 39 (LC-39) is a rocket launch site at the John F. Kennedy Space Center on Merritt Island in Florida, USA. The site and its collection of facilities were originally built for the Apollo program, and later modified to support Space Shuttle operations. NASA began modifying LC-39 in 2007 to accommodate Project Constellation. Launches from LC-39 are supervised from the Launch Control Center, located 3 miles (4.8 km) from the launch pads. LC-39 is one of several launch sites that share the Eastern Test Range.

Launch Complex 39 is composed of the two launch pads, the Vehicle Assembly Building (VAB), the Crawlerway (the route used by crawler-transporters to carry Mobile Launcher Platforms between the VAB and the pads), the Orbiter Processing Facility buildings, the Launch Control Center (which contains the firing rooms), a news facility (famous for the iconic countdown clock seen in television coverage and photos), and various logistical and operational support buildings.