The T-90 is the first Russian main battle tank fielded after the dissolution of the USSR. It was developed as a comprehensive upgrade of the mass-produced T-72, but with many of the newer technologies incorporated into the more advanced T-80 in the areas of armor protection and fire control. Superficially, the T-90 strongly resembles its two predecessors (particularly the T-72), with similar hull and turret layouts which followed traditional Soviet-era design principles. Notably however, the T-90 reverted to a standard diesel-powered engine as a result of deficiencies seen in the T-80’s gas turbine. As a result, the T-90 is slower and has a lower power-to-weight ratio, but compensates the shortcoming through greater engine reliability and fuel economy. The T-90 is also the first modern Soviet/Russian tank to feature a welded turret, although a traditional round cast turret was used initially. Armament consists of the same auto-loaded 125-mm 2A46M smoothbore found on the T-80, capable of firing the 9K119 (AT-11) ATGM. Protection is provided through composite armor as well as second-generation Kontakt-5 explosive reactive armor (ERA) which gives the turret its characteristic clam-shell appearance; the T-90 is the first Russian tank designed from the start with ERA. The T-90 was initially fitted with an advanced ATGM countermeasures suite known as Shtora-1 which includes a laser warning system, infrared jammers, and twin electro-optical/infrared dazzlers, one on each side of the gun, which resemble eyes. More modern variants include third-generation Relikt ERA, the Arena-M active protection system (APS), remote weapons stations, and even Western-style ammunition storage in the turret. Post Cold-War financing constraints prevented the T-90 to be built and fielded en masse by the Russian Army but it has obtained significant export success to Algeria, Azerbaijan, Turkmenistan and Uganda. India, however, is the world’s largest user with over 1,000 in service, including domestic production. The T-90 has seen combat in Russian service in the Second Chechen War as well as in the more recent invasion of Ukraine, where it has had somewhat better performance than its peers; it is estimated that around 175 T-90s were lost by the end of 2024 of which over two-thirds are modernized versions. This is proportionately much lower (relative to the pre-war active inventory) than the losses suffered by the T-72 or T-80. Numerous captured units have also been used in combat by Ukraine.

The original production T-90 (originally designated T-72BU) featured a cast turret entered service with the Russian Army in 1993, with a proposed export version designated T-90E but which was never built. Improvements led to the T-90A with a welded turret as well as a new engine and thermal viewer as well as a more advanced version of the 2A46 gun. An export version is known as the T-90S which is notable for lacking the laser dazzler 'eyes' of Russian variants. License-produced Indian versions of the T-90S are known as the Bhishma. A major export upgrade which first appeared in 2013 is known as the T-90MS which added third-generation Relikt ERA, slat armor, a hard-kill Arena APS, Sosna-U gunner sight, and a remote-controlled weapons station for its roof-mounted machine gun. It is the first Russian tank to provide amunition storage in the turret including blow-out panels to reduce the risk of a catastrophic explosion, as per Western practice. A further improved variant for domestic use is known as the T-90M and includes additional slat armor in the rear hull (which results in the removal of the external fuel tanks), a metal RPG net hanging under the turret, as well as changes to the autoloader to allow use of longer APFSDS rounds. It is currently the most advanced tank in Russian service and many have had additional 'cope cage' armor and anti-drone equipment added for combat in Ukraine. Non-tank variants include the BREM-72 armored recovery vehicle, MTU-90 bridge layer, IMR-3 combat engineering vehicle, and BMR-3 mine clearing vehicle. The BPMT tank support vehicle (described separately) is also based on the T-90 (or T-72) chassis.