A great martyr (also spelled greatmartyr or great-martyr) or megalomartyr (from Byzantine Greek μεγαλομάρτυς, megalomártus, from μέγας, mégas 'great' + μάρτυς, mártus 'martyr'; ; ; დიდმოწამე) is a classification of saints who are venerated in the Eastern Orthodox Church and those Eastern Catholic Churches which follow the Rite of Constantinople. The term is also used in Malta especially by parishes dedicated to Saint George in reference to him (San Ġorġ Megalomartri). Generally speaking, a greatmartyr is a martyr who has undergone excruciating tortures—often performing miracles and converting unbelievers to Christianity in the process—and who has attained widespread veneration throughout the Church. These saints are often from the first centuries of the Church, before the Edict of Milan. This term is normally not applied to saints who could be better described as hieromartyrs (martyred clergy) or protomartyrs (the first martyr in a given region).

Partial list of megalomartyrs