A missile is an airborne ranged weapon capable of self-propelled flight aided usually by a propellant, jet engine or rocket motor.

Historically, 'missile' referred to any projectile that is thrown, shot or propelled towards a target; this usage is still recognized today with any unguided jet- or rocket-propelled weapons generally described as rocket artillery. Airborne explosive devices without propulsion are referred to as shells if fired by an artillery piece and bombs if dropped by an aircraft.

Missiles are also generally guided towards specific targets termed as guided missiles or guided rockets. Missile systems usually have five system components: targeting, guidance system, flight system, engine, and warhead. Missiles are primarily classified into different types based on firing source and target such as surface-to-surface, air-to-surface, surface-to-air and air-to-air missiles.

Rockets were the precursor to modern missiles and the first rockets were used as propulsion systems for arrows as early as the 10th century in China. Usage of rockets as weapons before modern rocketry is attested to in China, Korea, India and Europe. In the 18th century, iron-cased rockets were used in India by the Kingdom of Mysore and Maratha Empire against the British which was developed into Congreve rocket and used in the Napoleonic Wars.

In the early 20th century, American Robert Goddard and German Hermann Oberth developed early rockets propelled by jet engines. In the 1920s, Soviet Union developed solid fuel rockets at the Gas Dynamics Laboratory. Later, the first missiles to be used operationally were a series of rocket based missiles developed by Nazi Germany during World War II including the V-1 flying bomb and V-2 rocket which used mechanical autopilot to keep the missile flying along a pre-chosen route. Less well known were a series of anti-ship and anti-aircraft missiles, typically based on a simple radio control (command guidance) system directed by the operator. However, these early systems in World War II were only built in small numbers. After World War II, the advent of the Cold War and development of nuclear weapons necessitated faster, accurate and versatile missiles with longer range and missile development was pursued by multiple countries.

Various attempts have been made to control the spread of long range missiles capable of carrying weapons of mass destruction, such as the Missile Technology Control Regime (1987) and the International Code of Conduct against Ballistic Missile Proliferation (2002). These were voluntary and not international treaties. Though not legally binding, more than 140 countries have been part of these agreements, and provide prior information on missile programs, expected launches, and tests. The gradual introduction of missile launched hypersonic glide vehicles since 2019, anti-satellite missiles, and the deployment of dual use missiles capable of carrying both conventional and nuclear warheads are proliferation concerns.

A missile is most often guided by a guidance system though there are missiles that are unguided during some phases of flight. Missile guidance refers to methods of guiding a missile to its intended target. Effective guidance is important because reaching the target position accurately and precisely is a critical factor for its effectiveness. The missile guidance system accomplishes this by four steps: tracking the target, computing the directions using tracking information, directing the computed inputs to steering control and steering the missile by directing inputs to motors or flight control surfaces. The guidance system consists of three sections: launch, mid-course and terminal with same or different systems employed across sections.

The guidance and homing systems are generally classified broadly into active, semi-active and passive. In active homing systems, the missile carries the equipment needed to transmit the radiation needed to illuminate the target and receive the reflected energy. Once the homing is initiated, the missile directs independently towards the target. In semi-active systems, the source of the radiation is located outside the missile usually in the launch vehicle which might be an aircraft or a ship and the missile will receive the radiation to direct towards the target. As the source is located outside, the launch vehicle needs to continue supporting the missile till it is guided to the intended target. In a passive system, the missile relies solely on the information from the target. The homing system might use light such as infrared, laser or visible light, radio waves or other electromagnetic radiation to illuminate the target. Once the guidance system identifies the target, the target might required to be tracked continuously if it is in motion. A guidance system might use INS which consists of a gyroscope and accelerometer or might use satellite guidance (such as GPS) to track the missile’s position relative to a known target. The missile computers will compute the flight path required to steer the missile towards the target. In command guidance, a human operator may operate it manually or a support or launch system will transmit commands by using either optic fiber or radio to guide the missile. The flight system uses the data from the targeting or guidance system to maneuver the missile in flight which might be accomplished using vectored thrust of engines or aerodynamic maneuvering using flight control surfaces such as wings, fins and canards.

Missiles are powered by propellants igniting to produce thrust and might employ types of rocket or jet engines. Rockets might be fueled by solid-propellants which are comparatively easier to maintain and enables faster deployment. These propellants contain a fuel and oxidizer mixed in select proportions with the grain size and burn chamber determining the rate and time of burn. Larger missiles might use liquid-propellant rockets where propulsion is provided by a single or combination of liquid fuels. A hybrid system uses solid rocket fuel with a liquid oxidizer. Jet engines are generally used in cruise missiles, most commonly of the turbojet type, because of their relative simplicity and low frontal area while turbofans and ramjets can also be theoretically used. Long-range missiles have multiple engine stages and might use similar type or a mix of engine types. Some missiles may have additional propulsion from another source at launch such as a catapult, cannon or tank gun.

Missiles have one or more explosive warheads, although other weapon types may also be used. The warheads of a missile provide its primary destructive power which might cause secondary destruction due to the kinetic energy of the weapon and unused fuel. Warheads are most commonly of the high explosive type, often employing shaped charges to exploit the accuracy of a guided weapon to destroy hardened targets. Warhead might carry conventional, incendiary, nuclear, chemical, biological or radiological weapons.

Missiles can be classified into categories by various parameters such as type, launch platform and target, range, propulsion and guidance system. Missiles are generally categorized into strategic or tactical missile systems. Tactical missile systems are short-range systems used to carry out a limited strike in a smaller area and might carry conventional or nuclear warheads. Strategic missiles are long-range weapons used to target beyond the immediate vicinity and are mostly designed to carry nuclear warheads though other warheads can also be fitted.

Strategic weapons are often classified into cruise and ballistic missiles. Ballistic missiles are powered by rockets during launch and follow a trajectory that arches upwards before descending to reach its intended target while cruise missiles are continuously powered by jet engines and travel at a flatter trajectory.

A ballistic missile is powered by single or multiple rockets in stages initially before following an unpowered trajectory that arches upwards before descending to reach its intended target. It can carry both nuclear and conventional warheads. A ballistic missile might reach supersonic or hypersonic speed and often travel out of the Earth's atmosphere before re-entry. It usually has three stages of flight:

• Boost phase: First phase at launch when one or more stages of rocket engine(s) fire propelling the missile
• Mid-course phase: Second phase when the rocket engines stop firing and the missile continues ascending upwards on the given trajectory
• Terminal phase: Final phase when the warhead(s) detach and descend towards the target

Ballistic missiles are categorized based on range as:

• Short-range : less than 1,000 kilometres (620 mi)
• Medium-range : 1,000 kilometres (620 mi) to 3,000 kilometres (1,900 mi)
• Intermediate-range : 3,000 kilometres (1,900 mi) to 5,500 kilometres (3,400 mi)
• Inter-continental : greater than 5,500 kilometres (3,400 mi)

A cruise missile is a guided missile that remains in the atmosphere and flies the major portion of its flight at a constant speed. It is designed to deliver a large warhead over long distances with high precision and are propelled by jet engines. A cruise missile can be launched from multiple platforms and is often self-guided. It flies at lower speeds (often subsonic or supersonic) and close to the surface of the Earth, which expends more fuel but makes it difficult to detect.

Missiles might be also be classified basis launch platform and target into surface-to-air, surface-to-surface, air-to-air, air-to-surface, anti-ship and anti-tank.

System	Abbreviation	Launch platform	Target
Anti-ship	AShM	Air/Land/Water	Water
Anti-tank	ATGM	Air/Land	Land
Air-to-air	AAM	Air	Air
Air-to-surface	ASM	Air	Land
Surface-to-air	SAM	Land	Air
Surface-to-surface	SSM	Land	Land
Anti-satellite	ASAT	Air/Land/Water	Space