枪管为枪械的主要组成零件之一，通常是以耐热不易变型的金属管打造而成，连接在膛室，当子弹被击发同时，因火药爆炸或气压所产生的膨胀气体，又或其他动力，会推动弹头通过枪管，最后成为高速的投射物射出。

如果子弹击发时，高动能的子弹无法顺利滑出枪管，便会造成所谓的「膛炸」，有足以致命的可能。其原因很多，例如枪支设计先天不良、枪管粗制滥造、枪管中有足以阻挡子弹射出的障碍物等等。其中最后一项可以透过日常保养避免，因此清理枪管是枪支维护的重点工作之一。

A gun barrel is the tube, usually metal, through which a deflagration or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity. Barrels are part of firearms and artillery pieces.

The first firearms were made at a time where metallurgy was not advanced enough to cast tubes able to withstand the explosive forces of early cannon, so the pipe (often actually built from staves of metal) needed to be braced periodically along its length, producing an appearance somewhat reminiscent of a storage barrel.