The Old English poem Beowulf is a particularly valuable source of information about early features of the English language. In its present form the poem is recorded in a manuscript of unknown provenance made, in all probability, shortly after the millennium. Yet it evinces linguistic features that are highly conservative, suggesting that the extant text was copied, perhaps directly, from a much older exemplar, and that the poem was composed in a more northerly dialect than the Late West Saxon one in which it is preserved. Some of the poem’s conservative linguistic features are detectable only on the basis of poetic meter. Other of the poem’s archaic features include some that are orthographic in nature: phonological, morphological, syntactic, lexical and metrical. Beowulf is not the only linguistically conservative poem preserved in Old English, but in many ways it reveals, more than any other poem, a great deal about what the language was like at a much earlier time than that at which all but a minuscule portion of the total extant corpus of Old English was recorded. It is thus an invaluable window on the prehistory of the English language.