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, 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. 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 Kontakt-5 reactive armor which gives the turret its noticeable clam-shell appearance (this would be later added to T-80s and T-72s as well). Additionally, the tank is 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. Although financing constraints have prevented the T-90 to be fielded en masse by the Russian Army, 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. Nevertheless, it has been criticized for failing to incorporate some of the more modern innovations seen in Western third-generation tanks, and retaining critical vulnerabilities such has having the ammunition stowed under the crew. 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 50 T-90s were lost in 2022 although 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. The more recent T-90M features improvements in nearly all areas including fire control, Relikt ERA, hard-kill Arena APS, and a remote-controlled weapons station for its roof-mounted machine gun. An export version is known as the T-90MS. 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.