An intercontinental ballistic missile, or ICBM, is a long-range (greater than 5,500 km (3,500 miles)) ballistic missile typically designed for nuclear weapons delivery, that is, delivering one or more nuclear warheads. However, new designs contemplated by the United States envision a conventional or even inert (non-explosive) payload, relying on the great speed at impact to cause significant damage. Due to their great range and firepower, in an all-out nuclear war, submarine and land-based ICBMs would carry most of the destructive force, with nuclear-armed bombers the remainder.

ICBMs are differentiated by having greater range and speed than other ballistic missiles: intermediate-range ballistic missiles (IRBMs), short-range ballistic missiles (SRBMs), and the newly-named theatre ballistic missiles. Categorizing missiles by range is necessarily subjective and the boundaries are chosen somewhat arbitrarily, and so exact boundaries between range classes are not (and never can be) authoritative except within a community which has agreed to a set of definitions.

All five of the nations with permanent seats on the United Nations Security Council have operational ICBM systems: all have submarine-launched missiles, and Russia, the United States and China also have land-based missiles. In addition, Russia and China have mobile land-based missiles.

India is developing the Surya ICBM after successfully test firing Agni-III IRBM. It is speculated by some intelligence agencies that North Korea is developing an ICBM; two tests of somewhat different developmental missiles in 1998 and 2006 were not fully successful.

In 1991, the United States and the Soviet Union agreed in the START I treaty to reduce their deployed ICBMs and attributed warheads.