A series of small spacecraft of the European Space Agency (ESA), to test new technologies for future use on larger missions. SMART-1 was launched on 27 September 2003 as the first ESA mission to the Moon, orbiting and conducting scientific observations. However, its main purpose is to test solar electric primary propulsion (SEPP), based on the use of xenon gas as a propellant and on power sourced from the spacecraft's solar arrays.

SMART-1 used the competing gravity of the Earth and the Moon to conserve the fuel supply, going into orbit around the Moon in November 2004 after a voyage lasting 14 months instead of a matter of a few days. The new propulsion system was used by ESA's BepiColombo mission to Mercury launched in 2018.