Grendel is a character in the Anglo-Saxon epic poem Beowulf. He is one of the poem's three antagonists, all aligned in opposition against the protagonist Beowulf. He is referred to as both an eoten and a þyrs, types of beings from wider Germanic mythology. He is also described as a descendant of the Biblical Cain and "a creature of darkness, exiled from happiness and accursed of God, the destroyer and devourer of our human kind." He is usually depicted as a monster or a giant, although his status as a monster, giant, or other form of supernatural being is not clearly described in the poem and thus remains the subject of scholarly debate. The character of Grendel and his role in the story of Beowulf have been subject to numerous reinterpretations and re-imaginings. Grendel is feared by all in Heorot but Beowulf, who kills both him and his mother.

Beowulf is an Old English epic poem in the tradition of Germanic heroic legend consisting of 3,182 alliterative lines. It is one of the most important and most often translated works of Old English literature. The date of composition is a matter of contention among scholars; the only certain dating is for the manuscript, which was produced between 975 and 1025 AD. Scholars call the anonymous author the "Beowulf poet". The story is set in pagan Scandinavia in the 6th century. Beowulf, a hero of the Geats, comes to the aid of Hrothgar, the king of the Danes, whose mead hall Heorot has been under attack by the monster Grendel for twelve years. After Beowulf slays him, Grendel's mother takes revenge and is in turn defeated. Victorious, Beowulf goes home to Geatland and becomes king of the Geats. Fifty years later, Beowulf defeats a dragon, but is mortally wounded in the battle. After his death, his attendants cremate his body and erect a barrow on a headland in his memory.