邮包炸弹指在邮包内藏有炸弹，一般是不法之徒制造，透过邮局或信差派送，用以恐吓及伤害收件人。邮包炸弹有时会由恐怖份子制造。一般邮包炸弹都会被设计成在开启时爆炸，期望严重伤害甚至杀害收件人。邮包炸弹可能有不规则形状。

另外在网络世界里，电邮巨型文件给其他人也被喻为邮包炸弹，因为这会造成收件人的电子邮箱爆满，以及下载严重耗时等种种问题。因此，若要电邮巨型文件给他人，一般可接受的做法是先将文件上载至某网页，然后将网址电邮给对方，让对方可以自行下载。

A letter bomb, also called parcel bomb, mail bomb or post bomb, is an explosive device sent via the postal service, and designed with the intention to injure or kill the recipient when opened. They have been used in Israeli targeted killings and in terrorist attacks such as those of the Unabomber. Some countries have agencies whose duties include the interdiction of letter bombs and the investigation of letter bombings. The letter bomb may have been in use for nearly as long as the common postal service has been in existence, as far back as 1764 (see Examples).