A Mars flyby is a movement of spacecraft passing in the vicinity of the planet Mars, but not entering orbit or landing on it. Unmanned space probes have used this method to collect data on Mars, as opposed to orbiting or landing. A spacecraft designed for a flyby is also known as a "flyby bus" or "flyby spacecraft".
One application of a Mars flyby is for a human mission, where after landing and staying on the surface for some time the ascent stage has a space rendezvous with another, unmanned spacecraft, thas was launched separately from Earth, flying by. Although this would require the ascent stage of the lander to reach the speed necessary to return to Earth (equal to that of the spacecraft flying by), the resources needed for Earth return would not have to enter or leave Mars orbit.
Alternately, a flyby-only human mission is also possible, without detaching at Mars, but to slingshot around Mars and back to Earth.
List of Mars flybys 
- Dawn, closest approach was 549 km.
- Rosetta within 250 km
- Mariner program spacecraft
- Mars program spacecraft
- Two Mars flyby attempts were made in 1960 under Mars 1M (Mars 1960A and Mars 1960B).
- The third attempt at a Mars flyby was the Soviet Mars 2MV-4 No.1, also called Mars 1962A or Sputnik 22, which launched in 1962 as part of the Mars program. but it was destroyed in low Earth orbit due to rocket failure.
- Mars 1 also launched in 1962 but communications failed before it reached Mars.
- Mars 4 achieved a flyby in 1974 and detected a nightside ionosphere.
- Mars 6 and 7 were Mars landers carried by instrumented flyby buses.
- Page 15-16 in Chapter 3 of David S. F. Portree's Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000, NASA Monographs in Aerospace History Series, Number 21, February 2001. Available as NASA SP-2001-4521.
- Space probe performs Mars fly-by - BBC
- Joseph A. Angelo - Encyclopedia Of Space And Astronomy (2006) - Page 171
- Astronautica - FLEM
- Washington Post, "Dennis Tito’s mission to Mars: Launching in 2018 for the children (and to beat China)", Brian Vastag, 27 February 2013
- Rayman, Marc D. "Dawn Journal: Aiming away from a bull's eye at Mars". The Planetary Society. Retrieved 2010-03-21.
- Malik, Tariq (February 18, 2009). "Asteroid-Bound Probe Zooms Past Mars". Space.com. Retrieved 2010-03-21.
- ESA - Rosetta successfully swings-by Mars,
- NSSDC - Nozomi
- McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 29 July 2010.
- Zak, Anatoly. "Russia's unmanned missions to Mars". RussianSpaecWeb. Retrieved 29 July 2010.
- Wade, Mark. "Mars". Encyclopedia Astronautica. Retrieved 29 July 2010.
- The Soviet Mars program, Professor Chris Mihos, Case Western Reserve University
- NASA - Mars 6