"Deor" (or "The Lament of Deor") is an Old English poem found in the late 10th century collection the Exeter Book. The poem consists of the lament of the scop Deor, who lends his name to the poem, which was given no formal title. Modern scholars do not actually believe Deor to be the author of this poem.

In the poem, Deor's lord has replaced him. Deor mentions various figures from Germanic mythology and reconciles his own troubles with the troubles these figures faced, ending each section with the refrain "that passed away, so may this." The poem consists of 42 alliterative lines.

Attempts at placing this poem within a genre have proven to be quite difficult. Some commentators attempting to characterise the work have called it an ubi sunt ("where are they?") poem because of its meditations on transience. It can also be considered a traditional lament and poem of consolation. Christian consolation poems, however, usually attempt to subsume personal miseries in a historical or explicitly metaphysical context (e.g., Boethius's Consolation of Philosophy), and such perspectives are somewhat remote from the tradition of Anglo-Saxon poetry. Medievalist scholars who have viewed the poem within the Anglo-Saxon tradition have therefore seen it primarily as a begging poem—a poem written by a travelling and begging poet who is without a place at a noble court—although because few other begging poems survive, assigning it to such a genre is somewhat speculative. Others have related "Deor" to other melancholy poems in the Exeter Book, such as "The Seafarer" and "The Wanderer".