With over five decades of service and a production run of around 80,000, the M113 family of tracked APCs is one of the most successful combat vehicles of all time, serving with distinction with dozens of armies around the world. The M113 was among the first vehicles to be produced with aluminum armor, which helped reduce its weight and allow it to be airlifted. It was operated by a two-man crew, and the original troop carrier could carry as many as 11 fully-equipped infantrymen, who could dismount through a power-operated ramp in the rear hull as well as a roof mounted hatch in the troop compartment. This compartment could also be used for a myriad of other uses, which allowed the M113 family to be employed in countless roles, many of which remain in US service long after the original APC was retired. The M113 is also fully amphibious and is propelled in the water with its tracks, but initial variants did not have NBC protection. The M113 began entering service with the US Army's new mechanized and armored cavalry units in the late 1950s and saw extensive combat in the Vietnam War; South Vietnamese forces also used it as an infantry fighting vehicle. Despite being gradually replaced by the M2 Bradley in the 1980s, the M113 still served in the Gulf War and non-APC variants continue to be in service with US forces to this day. Among the most notable was the M163 VADS (Vulcan Air Defense System) which was US's main late-Cold War SPAAG, but the shart range of the M61 Vulcan rotary cannon and the limited capabilities (range-only) of its AN/VPS-2 radar made it considerably inferior to contemporaries like the ZSU-23-4 or Gepard. Another variant was the M730 carrier vehicle for the M48 Chaparral SAM system. The M113 and its variants was adopted by as many of 50 foreign armed forces, notably NATO allies Belgium, Canada, Denmark, Greece, Netherlands, Norway, Portugal, and West Germany, while also being license produced by OTO Melara in Italy. Israel was also an extensive user of the M113 where it was used during the Six Day War and the Lebanon conflict.

Development began in 1956 and resulted in two prototypes, the T113 with aluminum armor, and the T117 with steel armor, the first of which was selected for production as the T113E1, later M113, in 1960. The M113A1 featured a diesel engine and further upgrades to the engine and suspension resulted in the M113A2. The last major modernization of the basic APC variant was the M113A3, which added an even more powerful engine, further mechanical improvements, as well as new driver controls, add-on armor, and external fuel tanks. These updates were added to previous variants as well as part of the RISE (Reliability Improved Selected Equipment) program. Non-APC versions were numerous, and include the M106 (107-mm), M1064 (120-mm), and M125 (81-mm) mortar carriers, the M163 VADS (Vulcan Air Defense System) anti-aircraft platform, M548 cargo carrier, M730 Chaparral SAM launcher, M557 and M1068 command posts, M901 ITV (Improved TOW Vehicle), M981 FISTV (Fire Support Team Vehicle), and M1059 smoke generating system. Additionally, a recovery vehicle was also produced based on the M113A2. Some M113 versions have also been used as mock BMP-2s for OPFOR exercises. Numerous foreign users have given their M113 enhanced combat capabilities in order them to be operated as IFVs, this includes the Italian-built VCC-1. Most export customers have adapted their M113s to local operational requirements as well.