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.
"Super Heavy Tank" - 130 tons. Purportedly one prototype was produced in 1944 and sent to Manchuria.
"Ultra Heavy Tank" - Modification of the O-1 Super Heavy Tank with four turrets. Project only.
Eighty ton tank - at least 1 prototype built in 1926. 80 tons with two 76 mm main guns and 4 machine guns
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 ton KV arming one 107mm gun and a 45 mm mounted next to the main gun), but none were made.
KV-5 Was a WW2 project to built a 100 ton KV tank arming a 107 mm ZiS-6M and a smaller turret arming a machine gun placed in front of the main turret, though none were built, only drawings remain of the tank
IS-7 - 1948 Soviet prototype super heavy tank. 68 metric tons, 1050hp diesel engine, 130mm main gun plus coaxial 14.5mm KPVT machine gun. 2 prototypes built.