Orion (Orion Multi-Purpose Crew Vehicle or Orion MPCV) is a partially reusable crewed spacecraft used in NASA's Artemis program. The spacecraft consists of a Crew Module (CM) space capsule designed by Lockheed Martin that is paired with a European Service Module (ESM) manufactured by Airbus Defence and Space. Capable of supporting a crew of four beyond low Earth orbit, Orion can last up to 21 days undocked and up to six months docked. It is equipped with solar panels, an automated docking system, and glass cockpit interfaces. Orion is launched atop a Space Launch System (SLS) rocket, with a tower launch escape system.

Orion was conceived in the early 2000s by Lockheed Martin as a proposal for the Crew Exploration Vehicle (CEV) to be used in NASA's Constellation program and was selected by NASA in 2006. Following the cancellation of the Constellation program in 2010, Orion was extensively redesigned for use in NASA's Journey to Mars initiative; later named Moon to Mars. The SLS became Orion's primary launch vehicle, and the service module was replaced with a design based on the European Space Agency's Automated Transfer Vehicle. A development version of Orion's crew module was launched in 2014 during Exploration Flight Test-1, while at least four test articles were produced. Orion was primarily designed by Lockheed Martin Space Systems in Littleton, Colorado, with former Space Shuttle engineer Julie Kramer White at NASA as Orion's chief engineer.

As of 2022^[update], three flight-worthy Orion spacecraft were under construction, with one completed and an additional one ordered, for use in NASA's Artemis program. The first completed unit, CM-002, was launched on November 16, 2022, on Artemis I.

The Trump administration has called for the termination of Orion spacecraft program after Artemis III.

Orion uses the same basic configuration as the Apollo command and service module (CSM) that first took astronauts to the Moon, but with an increased diameter, updated thermal protection system, and other more modern technologies. It is designed to support long-duration deep space missions with up to 21 days of active crew time plus 6 months' quiescent spacecraft life. During the quiescent period, crew life support would be provided by another module, such as the proposed Lunar Gateway. The spacecraft's life support, propulsion, thermal protection, and avionics systems can be upgraded as new technologies become available.

At launch, the Orion spacecraft includes both crew and service modules, a spacecraft adapter and an emergency launch abort system. The Orion's crew module is larger than Apollo's and can support more crew members for short or long-duration missions. The European service module propels and powers the spacecraft as well as storing oxygen and water for astronauts. Orion relies on solar energy rather than fuel cells, which allows for longer missions.

The Orion crew module (CM) is a reusable transportation capsule that provides a habitat for the crew, provides storage for consumables and research instruments, and contains the docking port for crew transfers. The crew module is the only part of the spacecraft that returns to Earth after each mission and is a 57.5° frustum shape with a blunt spherical aft end, 5.02 meters (16 ft 6 in) in diameter and 3.3 meters (10 ft 10 in) in length, with a mass of about 8.5 metric tons (19,000 lb). It was manufactured by the Lockheed Martin Corporation at Michoud Assembly Facility in New Orleans, Louisiana. It has 50% more volume than the Apollo capsule and will carry four astronauts. After extensive study, NASA selected the Avcoat ablator system to provide heat protection encountered during reentry for the Orion crew module. Avcoat, which is composed of silica fibers with a resin in a honeycomb made of fiberglass and phenolic resin, was formerly used on the Apollo missions and on the Space Shuttle orbiter for early flights.

The CM uses Glass cockpit digital control systems derived from those of the Boeing 787. It incorporates an "autodock" feature, like those of Progress, the Automated Transfer Vehicle, and Dragon 2, with provision for the flight crew to take over in an emergency. It has waste-management facilities, with a miniature camping-style toilet and the unisex "relief tube" used on the Space Shuttle. It has a nitrogen/oxygen (N
₂/O
₂) mixed atmosphere at either sea level (101.3 kPa or 14.69 psi) or reduced (55.2 to 70.3 kPa or 8.01 to 10.20 psi) pressure.