Luna 1, also known as Mechta (Russian: Мечта [mʲɪt͡ɕˈta], lit.: Dream), E-1 No.4 and First Lunar Rover, was the first spacecraft to reach the vicinity of Earth's Moon, the first spacecraft to leave Earth's orbit, and the first to be placed in heliocentric orbit. Luna 1 was launched as part of the Soviet Luna programme in 1959.

Initially intended as a Moon impactor, a malfunction in the ground-based control system caused an error in the upper stage rocket's burn time, and the spacecraft missed the Moon by 5,900 km (more than three times the Moon's radius). Nevertheless, Luna 1 became the first human-made object to reach heliocentric orbit and was dubbed "Artificial Planet 1" and renamed Mechta (Dream). Luna 1 was also referred to as the "First Cosmic Ship", in reference to its achievement of Earth escape velocity.

The satellite and rocket carrying Luna 1 was originally referred to as the Soviet Space Rocket by the Soviet Press. Pravda writer Alexander Kazantsev called it Mechta (Russian: Мечта, meaning 'dream'). Citizens of Moscow unofficially deemed it Lunik, a combination of Luna (Moon) and Sputnik. It was renamed to Luna 1 in 1963.

The spherical satellite was powered by mercury-oxide batteries and silver-zinc accumulators. There were five antennas on one hemisphere, four whip-style and one rigid, for communication purposes. The spacecraft also contained radio equipment including a tracking transmitter and telemetry system. There was no propulsion system.

Luna 1 was designed to impact the Moon, delivering two metallic pennants with the Soviet coat of arms that were included into its payload package. It also had six instruments to study the Moon upon its suicidal approach. The flux-gate magnetometer was triaxial and could measure ± 3000 gammas. It was designed to detect lunar magnetic fields. Two micrometeorite detectors, developed by Tatiana Nazarova of the Vernadsky Institute, were installed on the spacecraft. They each consisted of a metal plate with springs and could detect small impacts. Four ion traps, used to measure solar wind and plasma, were included. They were developed by Konstantin Gringauz. The scientific payload also included two gas-discharge Geiger counters, a sodium-iodide scintillation counter, and a Cherenkov detector. The upper stage of the rocket contained a scintillation counter and 1 kilogram (2.2 lb) of sodium for a gas-dispersion experiment.

The spacecraft weighed 361.3 kilograms (797 lb) at launch. It was about 1.22 metres (4.0 ft) in diameter.

Luna 1 was launched at 16:41 GMT (22:41 local time) on 2 January 1959 from Site 1/5 at the Baikonur Cosmodrome by a Luna 8K72 rocket. The first three stages operated nominally. The Soviet engineers did not trust automated systems for controlling the engine burns, so they communicated to the rocket via radio. The signal to stop firing the engine Block E stage was delayed, and the prolonged burn imparted an extra 175 m/s to Luna 1.

Consequently Luna 1 missed its target by 5,995 kilometers (3,725 mi). The spacecraft passed within 5,995–6,400 kilometers (3,725–3,977 mi) of the Moon's surface on 4 January after 34 hours of flight, and then became the first human made object to leave Earth's orbit on January 6, 1959. Luna 1 ran out of battery power on 5 January, when it was 597,000 kilometers (371,000 mi) from Earth, making it impossible to track further. The batteries were designed for a minimum of 40 hours but lasted for 62.