List of Mars orbiters

The following table is a list of Mars orbiters, consisting of space probes which were launched from Earth and are currently orbiting Mars. As of December 2016, there are fourteen known artificial satellites in Mars' orbit, six of which are active.

The Soviets' Mars program and NASA's Mariner program became the two first successful space programs that intended to explore Mars through orbiters. Mars 2, Mars 3 and Mariner 9 were all launched into space in May 1971, and all entered Mars’ orbit that same year. NASA's Mariner 9 reached the planet's orbit first on November 14, narrowly beating the Soviet's spacecraft amid the space race, and subsequently became the first spacecraft to orbit another planet.

Contact with all eight Mars orbiters launched during the 20th century has been lost. NASA's four spacecraft are conjectured to remain in Mars' orbit. Mariner 9, Viking 1 and Viking 2 are expected to lower down into the Martian atmosphere by 2022 and either burn up or crash into the planet's surface.Mars Global Surveyor is expected to crash onto the surface of the planet by 2047. The fate of the Soviet's three Mars program orbiters and Phobos 2 remains unclear, but they are still presumed to be in orbit.

2001 Mars Odyssey was launched April 7, 2001 on a Delta II rocket and currently holds the record for the longest-surviving continually active spacecraft in orbit around a planet other than Earth at 15 years, 5 months and 24 days.

In 2003, the European Space Agency (ESA) launched their first planetary mission with Mars Express to conduct reconnaissance and exploration of Mars from orbit. On 12 August 2005, NASA launched Mars Reconnaissance Orbiter (MRO). As MRO entered orbit in 2006, it joined three other active spacecraft which were in Mars' orbit: Mars Global Surveyor (MGS), Mars Express, and 2001 Mars Odyssey; at the time, this set a record for the most operational spacecraft in the immediate vicinity of Mars. MGS has since ceased to function.

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