The Altair spacecraft, previously known as the Lunar Surface Access Module or LSAM, is the planned lander spacecraft component of NASA's Project Constellation, which astronauts will use for landings on the Moon beginning around 2019.

On December 13, 2007, NASA's Lunar Surface Access Module was retitled "Altair", after the 12th brightest star in the night sky, Altair in the constellation Aquila. In Latin, "Aquila" means Eagle, providing a connection to the first crewed lunar lander, Apollo 11's Eagle.

Altair, which is similar in design to (but much larger than) the Apollo Lunar Module (LM), will consist of two stages: a descent stage, which will house the majority of the fuel, power supplies, and breathing oxygen for the crew, and an ascent stage, which will house the astronauts, life-support equipment, and fuel for the ascent stage motor and steering rockets. Like the Apollo LM, Altair's crew module is based on a sideways cylinder, but unlike its two-man Apollo ancestor, Altair is designed to carry the entire four-man mission crew to the surface while the Orion Spacecraft remains unmanned in lunar orbit. It will also be flown unmanned, similarly to the Apollo Applications Program's LM Truck concept, but without having to fly a manned Orion spacecraft out to the Moon.