殉教，又称殉道，意指为了宗教或信仰而不畏迫害和杀戮，以致牺牲生命。

最初无论是圣经还是世俗界，殉教者（martyr）一词的意思都是目击者。其新的意义取自耶稣受难。于是早期基督徒认为是殉道者的原型。

天主教认为第一个为教会殉教的基督徒是斯德望，圣经使徒行传中记载，他因为传讲耶稣基督是弥赛亚被犹太人用石头砸死。但是天主教教义着重尊重生命，更反对用自杀的方式来表现对信仰的维护。这原意原则上要避免不必要的生命冒险。但是教义中又强调基督徒不应以言行「为主作证为耻」。基督徒认为殉教者是为死而复活的基督作证，他们与基督因爱德而结合，为信仰真理和基督的道理而作证，因勇毅而忍受死亡。

A martyr (Greek: μάρτυς, mártys, "witness"; stem μάρτυρ-, mártyr-) is somebody who suffers persecution and death for advocating, renouncing, refusing to renounce, or refusing to advocate a belief or cause as demanded by an external party. This refusal to comply with the presented demands results in the punishment or execution of the martyr by the oppressor. Originally applied only to those who suffered for their religious beliefs, it is now often used for people imprisoned or executed for espousing a political cause.