Super-heavy tanks are armoured fighting vehicles of very large size, generally over 75 tonnes. Programs have been initiated on several occasions with the aim of creating an invincible vehicle for penetrating enemy formations without fear of being destroyed in combat; however, only a few examples have ever been built, and there is no clear evidence any of these vehicles saw combat. Examples were designed in World War I and World War II, along with a few in the Cold War.
The first super-heavy tank was designed by the Russian naval engineer Vasily Mendeleyev who worked on the project from 1911 to 1915. The tank was envisioned to be invulnerable to almost all contemporary threats but remained on paper because of its high construction cost. It was followed by the British Flying Elephant concept as a way to break through any potential defensive line, and the German K-Wagen (Großkampfwagen). Two of them were under construction when the war ended and both were demolished.
During World War II all of the major combatants introduced prototypes for special roles. Adolf Hitler was a proponent of "war winning" weapons and supported projects like the 188 tonne Maus, and even larger 1,000 tonne Landkreuzer P. 1000 Ratte and 1,500 tonne Landkreuzer P. 1500 Monster. The British, Soviets and Americans all built prototype designs similar to the Jagdtiger, but none of these saw combat as the need for such a weapon turned out to be extremely limited.
The idea of super-heavy tanks saw less development after the war, except in the Soviet Union where some relatively heavy tank prototypes were tested for the Cold War nuclear battlefield, one example being the Object 279. These may be considered super-heavy by the standards of Soviet tank design, where the emphasis was on small size and low weight, but they were no heavier than the contemporary U.S. and British heavy tanks of the period.
T28 Super Heavy Tank - Heavily armoured self-propelled gun (86 tons). Development started in 1943, with 25 vehicles planned for production that year. 2 prototypes built/passed trials, but never saw action. The T28 was re-designated as the T105 mm Gun Motor Carriage T95 in 1945.
T-42 (Tank Grote or TG-V) - 100 tons with 107 mm main gun and four sub-turrets. One prototype made - 1932 
KV-4 - WWII supertank project. A proposed 90-100 ton tank, carrying a 107 mm main gun and a 45 mm or 76 mm secondary; various layouts were considered, with the hull-mounted 107 mm an a 76 mm turret chosen as the final option.
KV-5 - another Kliment Voroshilov series 100-ton-class tank. Armed with the same 107 mm main gun in a large, KV-2-style turret, and two 12.7 mm machine gun turrets (one on the forward hull, one on top of the main turret); powered by two V2 diesels due to wartime lack of a 1200 hp engine.
IS-7 - 1948 Soviet prototype super heavy tank. 68 metric tons, 1050hp diesel engine, 130mm main gun developed from main armament of Soviet destroyers, one 14.5 and two 7.62 mm co-axial guns.