Beowulf: the Monsters and the Critics is an important 1936 lecture given by J. R. R. Tolkien on the subject of Beowulf criticism. It was published in 1983 in The Monsters and the Critics.
This paper is widely regarded as a formative work in early 20th century Beowulf studies; some claim that without it, the poem, Beowulf, might not be studied today. In this talk, Tolkien speaks against critics who play down the fantastic elements of the poem (Grendel, Grendel's Mother, the dragon, etc.) in favor of using Beowulf solely as a source for Anglo-Saxon history. Tolkien argues that rather than being merely extraneous, these elements are key to the narrative and should be the focus of study. Later critics who disagreed with Tolkien on this point have routinely had to cite him and systematically defend their arguments.
This lecture is available in several book forms including:
Nicholson, Lewis E. (Ed.) (1963). An Anthology of Beowulf Criticism. Notre Dame: University of Notre Dame Press. ISBN 0268000069