史诗是一种庄严的文学体裁，内容为民间传说或歌颂英雄功绩的长篇叙事诗，它涉及的主题可以包括历史事件、民族、宗教或传说。

Albert Lord和Milman Parry主张经典的史诗基本上是口传形式流传的。在文本尚未出现时，史诗最初是纯口述式记录的，在传达过程中，听众聆听史诗后，会用口述形式将史诗世代相传，随着时间而增添情节，最后被整理、加工，以文本记载成为一部统一的作品。这类史诗的代表有荷马的史诗作品《伊利亚特》和《奥德赛》。另一种为文学作家以特定的观念目的有意识地编写而成的「文学史诗」，这类史诗的代表有维吉尔的《埃涅阿斯纪》和约翰·弥尔顿的《失乐园》。 epyllion是另一种篇幅简短的史诗，字源来自古希腊文ἐπύλλιον，意思是「小的史诗」。epyllion一词在十九世纪开始被使用，其叙述的内容通常是浪漫或神话的主题，经典的epyllion例子包括《埃涅阿斯纪》第六卷中关于Nisus和Euryalus的故事。另外，epyllion亦指一些英国文艺复兴时期的诗，特别是那些受奥维德影响的作品。

An epic poem, epic (from Latin epicus, from the Ancient Greek adjective ἐπικός, epikos, from ἔπος, epos, "word, story, poem"), epos (from Latin epos, from Greek ἔπος, epos), or epopee (from French épopée, from neo-Latin epopoeia ) is a lengthy narrative poem, ordinarily concerning a serious subject containing details of heroic deeds and events significant to a culture or nation. Milman Parry and Albert Lord have argued that the Homeric epics, the earliest works of Western literature, were fundamentally an oral poetic form. These works form the basis of the epic genre in Western literature. Nearly all Western epic (including Virgil's Aeneid and Dante's Divine Comedy) self-consciously presents itself as a continuation of the tradition begun by these poems. Classical epic employs dactylic hexameter and recounts a journey, either physical (as typified by Odysseus in the Odyssey) or mental (as typified by Achilles in the Iliad) or both. Epics also tend to highlight cultural norms and to define or call into question cultural values, particularly as they pertain to heroism.