A ballistic missile is a type of missile that follows a ballistic trajectory and is powered only during a relatively brief initial period—most of the flight is unpowered. Short-range ballistic missiles (SRBM) typically stay within the Earth's atmosphere, while most larger missiles travel outside the atmosphere. The type of ballistic missile with the greatest range is an intercontinental ballistic missile (ICBM). The largest ICBMs are capable of full orbital flight.

These missiles are in a distinct category from cruise missiles, which are aerodynamically guided in powered flight and thus restricted to the atmosphere.

One modern pioneer ballistic missile was the A-4, commonly known as the V-2, developed by Nazi Germany in the 1930s and 1940s under the direction of Wernher von Braun. The first successful launch of a V-2 was on October 3, 1942, and it began operation on September 6, 1944, against Paris, followed by an attack on London two days later. By the end of World War II in Europe in May 1945, more than 3,000 V-2s had been launched. In addition to its use as a weapon, a vertically launched V-2 became the first human-made object to reach outer space on June 20, 1944.

The R-7 Semyorka was the first intercontinental ballistic missile.

The largest ballistic missile attack in history took place on 1 October 2024 when the Iranian Revolutionary Guard launched about 200 missiles at Israel, a distance of about 1,500 kilometers. The missiles arrived about 15 minutes after launch. It is believed that Iran's Fattah-1 and Kheybar Shekan missiles were used, which both have a range of about 1,400 km.

In order to cover large distances, ballistic missiles are usually launched into a high sub-orbital spaceflight; for intercontinental missiles, the highest altitude (apogee) reached during free-flight is about 4,500 kilometers (2,800 mi). A ballistic missile's trajectory consists of three parts or phases: the boost phase, the mid-course phase and the terminal phase. Special systems and capabilities are required to facilitate the successful passage from one phase to the other.

The boost phase is the powered flight portion, beginning with the ignition of the engines and concluding with the end of powered flight. The powered flight portion can last from a few tenths of seconds to several minutes and can consist of multiple rocket stages. Internal computers keep the missile aligned on a preprogrammed trajectory. On multi-stage missiles, stage separation (excluding any post-boost vehicles or MIRV bus) occurs primarily during the boost phase.

The mid-course phase is the longest in the missile's trajectory, beginning with the conclusion of powered flight. When the fuel is exhausted, no more thrust is provided and the missile enters free flight. During this phase the missile, now largely consisting of a warhead or payload and possibly defensive countermeasures and small propulsion systems for further alignment toward its target, will reach its highest altitude and may travel in space for thousands of kilometres (or even indefinitely, in the case of some fractional-orbital capable systems) at speeds of up to 7.5 to 10 kilometres per second (4 to 5 nautical miles per second).