The Christian Martyrs' Last Prayer, by Jean-Léon Gérôme (1883).
A martyr is someone who suffers persecution and later assassination or death for advocating, renouncing (giving up), or refusing to renounce (not giving up) a religious belief or other cause, despite another person or group demanding that they do so.
Originally it was applied only to those who suffered for their religious beliefs but now the term has come to be used in connection with people killed for a political or nationalist cause as well.
Famous examples of people considerd religious martyrs
2015: 21 construction workers who were in the Coptic Orthodox Church except for one, are killed by the Islamic State(IS) because they believed in Jesus Christ. These are the names of the 21 martyrs: