飞弹(Missile)，是本身有动力、有诱导能力且在空气或是太空中移动的弹药。有诱导能力但没有动力的弹药称作导引炸弹，有动力但是没有诱导能力的弹药称作火箭弹。

在导弹的制导的分类上通常有两类，一种是信号发送媒体的不同，如：有线导引、雷达导引、红外线导引、雷射导引、电视导引等。另外一种分类是飞弹的制导方式的不同，如：惯性导引、乘波导引、主动雷达导引和指挥至瞄准线导引等。

按照导弹的作用分类可以简单地分为战略导弹和战术导弹。

飞弹的分类原则是由两个部分所构成：发射载具的特性与攻击目标的性质。发射载具的特性包括：空射，面射，潜射，舰射等。攻击的目标性质包括：对空，对面，对潜，对舰。把这两项原则合并在一起就是目前最常见的各类飞弹的分类系统。虽然发射载具是飞弹分类的一项原则，不过同一种飞弹往往可以在简单的改装下自不同的载具上发射，因此许多飞弹往往会在不同的类别当中重复出现。譬如说鱼叉反舰飞弹可以自潜艇、水面舰艇与飞机上发射，因此它会分别出现在潜射反舰飞弹、舰射反舰飞弹以及空射反舰飞弹当中。

In modern usage, a missile is a self-propelled precision-guided munition system, as opposed to an unguided self-propelled munition, referred to as a rocket (although these too can also be guided). Missiles have four system components: targeting and/or missile guidance, flight system, engine, and warhead. Missiles come in types adapted for different purposes: surface-to-surface and air-to-surface missiles (ballistic, cruise, anti-ship, anti-tank, etc.), surface-to-air missiles (and anti-ballistic), air-to-air missiles, and anti-satellite weapons. All known existing missiles are designed to be propelled during powered flight by chemical reactions inside a rocket engine, jet engine, or other type of engine. Non-self-propelled airborne explosive devices are generally referred to as shells and usually have a shorter range than missiles.