Cædmon (/ˈkædmən, ˈkædmɒn/; fl. c. 657–684) is the earliest English poet whose name is known. A Northumbrian cowherd who cared for the animals at the double monastery of Streonæshalch (now known as Whitby Abbey) during the abbacy of Hilda, he was originally ignorant of "the art of song" but learned to compose one night in the course of a dream, according to the 8th-century Christian historian and saint Bede. He later became a zealous monk and an accomplished and inspirational Christian poet. He is venerated as a saint in the Eastern Orthodox Church, Roman Catholicism and Anglicanism, with a feast day on 11 February.

Cædmon is one of twelve Anglo-Saxon poets identified in medieval sources, and one of three of these for whom both roughly contemporary biographical information and examples of literary output have survived. His story is related in the Historia ecclesiastica gentis Anglorum ("Ecclesiastical History of the English People") by Bede, who wrote, "[t]here was in the Monastery of this Abbess a certain brother particularly remarkable for the Grace of God, who was wont to make religious verses, so that whatever was interpreted to him out of scripture, he soon after put the same into poetical expressions of much sweetness and humility in Old English, which was his native language. By his verse the minds of many were often excited to despise the world, and to aspire to heaven."

Cædmon's only known surviving work is Cædmon's Hymn, a nine-line alliterative vernacular praise poem in honour of God. The poem is one of the early attested examples of Old English and is, with the runic Ruthwell Cross and Franks Casket inscriptions, one of three candidates for the earliest attested example of Old English poetry. It is also one of the early recorded examples of sustained poetry in a Germanic language. In 1898, Cædmon's Cross was erected in his honour in the graveyard of St Mary's Church in Whitby.

The sole source of original information about Cædmon's life and work is Bede's Historia ecclesiastica. According to Bede, Cædmon was a lay brother who cared for the animals at the monastery Streonæshalch (now known as Whitby Abbey). One evening, while the monks were feasting, singing, and playing a harp, Cædmon left early to sleep with the animals because he knew no songs. The impression clearly given by Bede is that he lacked the knowledge of how to compose the lyrics to songs. While asleep, he had a dream in which "someone" (quidam) approached him and asked him to sing principium creaturarum, "the beginning of created things." After first refusing to sing, Cædmon subsequently produced a short eulogistic poem praising God, the Creator of heaven and earth.

Upon awakening the next morning, Caedmon remembered everything he had sung and added additional lines to his poem. He told his foreman about his dream and gift and was taken immediately to see the abbess, believed to be Hilda of Whitby. The abbess and her counsellors asked Cædmon about his vision and, satisfied that it was a gift from God, gave him a new commission, this time for a poem based on "a passage of sacred history or doctrine", by way of a test.

When Cædmon returned the next morning with the requested poem, he was invited to take monastic vows. The abbess ordered her scholars to teach Cædmon sacred history and doctrine, which after a night of thought, Bede records, Cædmon would turn into the most beautiful verse. According to Bede, Cædmon was responsible for a large number of splendid vernacular poetic texts on a variety of Christian topics.

After a long and zealously pious life, Cædmon died like a saint: receiving a premonition of death, he asked to be moved to the abbey's hospice for the terminally ill where, having gathered his friends around him, he died after receiving the Holy Eucharist, just before nocturns. Although he is often listed as a saint, this is not confirmed by Bede and it has been argued that such assertions are incorrect.

The details of Bede's story, and in particular of the miraculous nature of Cædmon's poetic inspiration, are not generally accepted by scholars as being entirely accurate, but there seems no good reason to doubt the existence of a poet named Cædmon. Bede's narrative has to be read in the context of the Christian belief in miracles, and it shows at the very least that Bede, an educated and intelligent man, believed Cædmon to be an important figure in the history of English intellectual and religious life.