The T-64 was the direct successor to the venerable T-54/55 series (both designed by Alexander Morozov) and was a significant improvement over the T-62, being the first design designated as a main battle tank by Soviet authorities. The T-64 borrowed the traditional hull and turret layout of Soviet Cold War tanks but featured numerous innovations. One was the incorporation of composite armor known as 'Combination K'. This was composed of two outer layers of steel with a middle layer of glass-reinforced plastic. The T-64 was the first tank in the world to use composite armor which gave it a considerable edge in protection against its NATO contemporaries and also helped keep weight low. The T-64 is also notable for having smaller-diameter road wheels with rollers. Armament consisted of a 125-mm D-81T smoothbore gun, which was rushed into service due to fears of earlier Soviet tanks being outgunned by the new British L7 gun which became the NATO standard in the 1960s. It was also seen as necessary to penetrate the improved armor of tanks like the M60 and Chieftain. A further novelty was the incorporation of a carousel autoloader which reduced the crew to just three, although the need to stow ammunition under the turret crew was a major vulnerability (one which was inherited by all subsequent Soviet/Russian tanks). Later versions were also able to fire ATGMs from the gun, a feature which has since become standard on Soviet and Russian tanks. Unfortunately, the sophistication of the T-64 was such that it became terribly expensive to build in mass numbers, to this was added an excessively complex engine, unreliable suspension, and an autoloader that was dangerous to crews. As a result, the T-64 was used primarily to equip elite Red Army units such as the Group of Soviet Forces stationed in East Germany (GSFG) that would have formed the front line against any attack on NATO while the T-62 equipped motor rifle divisions and the subsequent (cheaper) T-72 used for lower category tank divisions. The tank’s expense also meant that it became the only post-WW2 Soviet tank not to be exported, even to its Warsaw Pact allies, although Belarus, Uzbekistan and Ukraine were left with former Soviet stocks after the dissolution of the USSR. Modernized Ukrainian T-64s have seen considerable action in the Donbas in 2014 and during the Russian invasion of 2022, being the most widely available tanks in the country's inventory. It is estimated that around 300 were lost in the battles against separatist and Russian forces in 2014-15 although their performance after the 2022 invasion has been much better thanks to vastly improved training and tactics, with only around 250 lost during 2022 despite much higher intensity of combat. Large losses among Russia's newer tanks have also forced it to deploy T-64s in storage to the front lines as well.

The original T-64 (Ob’yekt 432) was fitted with the D-68 115-mm gun of the T-62, however, this was quickly switched to the larger caliber D-81T in the T-64A that also added side skirts and improved suspension. The next major variant was the T-64B, with upgraded armor and fire control systems as well as the 2A46M-1 gun of the T-72 and T-80 (however, the original autoloader was kept) with the ability to fire 9K112 (AT-8) missiles. Sub-variants known as the T-64BM had more powerful 1,000-hp engines, while the T-64BV had Kontakt-1 ERA on the glacis plate, hull sides and turret. A Ukrainian modernization program resulted in the T-64U and later T-64BM Bulat, which added more advanced ERA, 9K119 (AT-11) missiles, and upgraded equipment in order to bring it to the standard of the T-84. Only a small number have been modified to this standard, however. The BREM-64 armored recovery vehicle was also built in small numbers.