The T-55 medium tank has a fully tracked, five-road-wheeled chassis. This chassis has a space between the first and second road wheels and no return rollers. The T-55 has a low-silhouetted hull with a dome shaped turret mounted over the third road wheel. It is armed with a 100-mm rifled gun, which has a bore evacuator at the muzzle.

The T-55 also mounts a 7.62-mm coaxial machine-gun. Early versions also mounted a bow-mounted 7.62-mm machine-gun. The T-55 differs from the older T-54 models because it lacks the right-hand cupola and the turret dome ventilator, which is located in front of that cupola on the T-54.

Most T-55's also lack the turret-mounted 12.7-mm antiaircraft machine-gun of the T-54. All T-55's mount an infrared gunner's searchlight above, and to the right of the main gun. This searchlight, however, is not a distinguishing feature since it has been retrofitted to many T-54 and T-54A tanks.

The T-55 combines a high velocity gun with a highly mobile chassis, a low silhouette, and exceptional long-range endurance. Improvements over the T-54 include a larger V-12 water-cooled diesel engine with 580 rather than 520 hp, and an increased cruising range of 500 rather than 400 kilometers (600 kilometers with auxiliary tanks). The increased cruising range can go up to 715 kilometers with two 200-liter auxiliary fuel tanks which can be carried on the rear. The T-55 has two-plane stabilization of the main gun rather than vertical stabilization only. It also has a basic load for the main gun of 43 rather than 34 rounds.

The T-55 can ford depths of 1.4 meters without preparation. It has snorkel equipment which enables it to cross depths of up to 5.5 meters at a speed of 2 kilometers per hour. This equipment takes about 30 minutes' preparation, but can be jettisoned immediately on leaving the water. All T-55's have the PAZ radiation detection system; the T-55A also has an anti-radiation liner. Injecting vaporized diesel fuel onto the exhaust system can generate a dense smoke screen.

T-54A Same as the T-54 but introduced the D-10TG gun with a new fume evacuator, and vertical plane stabilization system. Internal improvements included a new multi-stage air cleaner and radiator controls for improved engine performance. China manufactured this variant under license as the Type 59.

T-54B This version introduced the OU-3 Infrared searchlight on the commander's cupola, and a TPN-1 gunner's day/night sight in place of the earlier MK-4 periscope. This version also introduced a two-axis stabilization system and the improved D-10T2S 100-mm rifled gun. This was the first version to be regularly equipped with a snorkel to allow deep fording of rivers.

T-54K This is the command version of the T-54A. It incorporates an additional radio by reducing the ammunition storage.

T-54AD This is a Polish-built command version of the T-54 that incorporates a slight extension of the turret that provides space for the additional radios.

OT-54 This flame-thrower tank substituted a ATO-1 automatic flame-thrower for the 7.62-mm coaxial machine-gun. The bow ammunition storage was modified to permit carrying 460-liters of flammable liquid using compressed gas for propulsion. Maximum range was 160 meters and the system could fire 15-20 bursts per minute.

T-55 The T-55 used a new turret, similar to that used on the T-54A, but without the prominent roof-top "mushroom" ventilator dome, and two enlarged "D" roof panels. Internal improvements include the V-55 engine, initial stages of the PAZ chemical/radiation protection system, and an increase of ammunition to 43 rounds. This tank does not have a 12.7-mm antiaircraft DShK machine-gun on the loader's hatch.

T-55A This variant incorporated the complete PAZ/FVU chemical/radiation filtration system. This version is most easily recognized by the larger combings on the commander's and loader's hatches as well as the blister on the driver's hatch.

T-55A Model 1970 This version is equipped with a 12.7-mm antiaircraft DShK machine-gun.

T-55A Model 1974 This version is equipped with the KTD-2 laser rangefinder, which is mounted immediately above the main gun in an armored box.

T-55K There are three variants of this command tank. These vehicles have an additional command radio as well as supporting generator, and carry less ammunition. The T-55K1 and T-55K2 both carry two R-123 or R-123M and a R-124. The T-55K3 carries one R-130M, a R-123, a R-124, and a 10-meter antenna. Command variants of the later variants carry the same designations, e.g., T-55MK1, T-55AM1K3, etc.

OT-55 This flame-thrower tank incorporates the ATO-200 flame projector. The flame thrower is ignited by pyrotechnic charges, and 12 charges are the basic load. The stowage tank contains 460-liters of flammable liquid, and each burst averages 36 liters. The maximum effective range of the system is 200 meters, with the stream having an initial muzzle velocity of 100 m/s.

T-55MV This is the T-55M with its armor protection supplanted with a first generation explosive reactive armor (ERA) array. Most of these vehicles were also retrofitted with the same fire-control improvements of the T-55AM2PB, including the AT-10 STABBER antitank guided missile, the Volna FCS, as well as the automotive and communications improvements.

T-55AMV This is the T-55AM with the same ERA protection as the T-55MV. Most of these tanks also received the same improvements of the T-55AM2PB.

T-55AM1 This is the modernized version of the T-55 with improved fire controls. The Czechoslovak version uses a laser rangefinder mounted over the main gun and a wind sensor. The FSU version incorporates the KTD-2 or KDG-1 laser rangefinder. The Polish version uses a new fire control system that integrates a laser rangefinder into the gunner's sight.

T-55AM2 This is the improved T-55AM1 with the BDD (horse-shoe) appliqu? armor. These BDD armor panels consist of armored steel boxes filled with penapolyurethane. Cavities in the boxes can be supplemented with water or sand for added protection. This version also incorporates the improved V-55U engine that has an integral supercharger and offers 620 hp. This tank has also been retrofitted with the improved R-173P radio system.

T-55AM2PB This is the T-55AM2 with fire control improvements and the AT-10 STABBER antitank guided missile. It also incorporates the 1K13 BOM gunner's sight in place of the TPN-1M sight, and the new Volna fire control system that includes the KDT-2 laser rangefinder, the BV-55 ballistic computer, the TShSM-32PB sight and the Tsiklon-M1 gun stabilization system.

Type 59 This is the Chinese produced copy of the T-54A. Later improvements include the addition of a laser rangefinder over the main gun and the addition of side skirts.

Type 59-II This is the Type 59 armed with a 105-mm main gun, believed to be derived from the standard NATO 105-mm rifled gun. The gun has a bore evacuator and a segmented thermal sleeve.

Type 62 Although externally very similar to the Type 59, this tank is in fact a scaled-down light tank patterned after the Type 59. It is armed with an 85-mm gun and is more thinly armored.

Type 69-I This is a product improved version of the Type 59 that is armed with an improved 100-mm smoothbore gun that is distinguishable by its bore evacuator, located farther back on the tube than the usual 100-mm rifled gun.

Type 69-II This is the more common version of the Type 69 family. This version is equipped with the normal 100-mm rifled gun. This tank incorporates the TSFC 2-axis gun stabilization, a new Type 70 gunner's sight, full active infrared night fighting equipment, and engine smoke discharger, an NBC protective system, and a laser rangefinder. The Type 69-II can be distinguished from the earlier Type 59 by the rear engine plate that has a small elliptical bulge for the cooling fan. This version also has the driver's headlights mounted in two pairs on the fenders, not on the hull glacis. Some of these tanks were also outfitted with "Boom Shield" stand-off armor baskets on the turret.

Type 69-IIC This is the command version of the Type 69-II. This tank is equipped with an additional command radio and long radio aerial. It can also be identified by the presence of a long tube welded to the turret top for the radio aerial and two stowage boxes on the hull rear, one of which contains cabling and a field phone.

Type 79 (Type 69-III) This is a Type 69-II equipped with a 105-mm rifled gun.

Type 80 This is an upgraded Type 79 with a new suspension. A further improved version, the Type 80-II incorporates further automotive improvements.

Ti-67 These modifications include replacing the 100-mm gun by a 105-mm M68 rifled gun, ammunition racks modified to accept 105-mm ammunition, new communications equipment, commander's seat modified, gunner's seat replaced, installation of azimuth indicator, driver's hatch can now be opened from the outside, commander's traverse control installed, sighting system modified for 105-mm ammunition, replacing the coaxial machine gun by a 7.62-mm (0.30) Browning machine gun and the 12.7-mm DShKM anti-aircraft machine gun by a 12.7-mm (0.50) Browning M2 HB machine gun, new fire control and electrical system, air-conditioning system, new radio mounts on turret rear, American infantry telephone on hull rear, Browning 0.30 machine gun at loader's station, exhaust outlet angled upwards, additional track stowage, fire-extinguishing system installed and new night vision equipment.

Ti-67 Model S In addition to all of the previous modifications, this is the Ti-67 with many other improvements including the American Detroit Diesel 8V-71T engine developing 609 hp, new semi-automatic hydromechanical transmission equipped with a torque converter, new air cleaners, Blazer explosive reactive armor added to the hull and turret, Cadillac Gage Textron weapon stabilization system, installation of EL-OP computerized Matador fire control system, new low-profile commander's cupola, infra-red detectors, passive night vision equipment for commander, gunner and driver, Spectronix fire detection and suppression system, new turret basket and extensive external stowage, modernized driver's station including replacement of sticks by a steering wheel, new final drives, new fuel system with all fuel now internal and improved suspension.

TR-580 (TR-77) This is a variant of the T-55 using a lengthened hull and a new suspension system with spoked wheels.

TR-85 (TR-80 or TR-800) This is a drastically modified version of the T-55 with a new turret, a new German diesel engine and a completely redesigned suspension.