火星塞，又称为火星塞或火嘴，火花塞大多数情况下是指汽油引擎的一个重要零件。

火花塞（Spark Plug）是安装在内燃机中燃烧室的顶端，大多数的原厂火星塞都是以镍锰合金作为电极材料，如需更耐用和更佳的点火效果可用铂甚至铱等贵金属制造。火花塞是用于产生电火花以引燃压缩后经雾化的汽油和空气混合物的组件。通常火花塞头部的中心接点由绝缘良好的线缆连接到产生高压的点火线圈，而火花塞的外壳接地并在前端焊接弯曲接地电极，与中心电极形成一个微小的空隙。在点火线圈产生的高压下，这个空隙间会产生电弧。最早商用的火花塞设计专利是博世公司在1902年申请的。它的出现使得内燃机的实现成为可能。

A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. The central electrode, which may contain a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto. The spark plug's metal shell is screwed into the engine's cylinder head and thus electrically grounded. The central electrode protrudes through the porcelain insulator into the combustion chamber, forming one or more spark gaps between the inner end of the central electrode and usually one or more protuberances or structures attached to the inner end of the threaded shell and designated the side, earth, or ground electrode(s).