Old English is a very different language from modern English, and was spoken from the fifth into the twelfth century. It was a northern Germanic language, and later was influenced by Old Norse after the Viking invasions of the ninth and tenth centuries. It was also influenced by Latin, as the influence of Christianity grew, and the presence of clergy who knew Latin increased. It originally had a series of grammatical cases, as Latin and Greek did, but eventually these began to die out.
There were four main dialects of Old English - Mercian, Northumbrian, Kentish, and West Saxon, but the Wessex Dialect spoken by Alfred the Great became dominant after he unified Anglo-Saxon England in 878.
Old English was originally written using the Futhorc variation of the Runic alphabet. Runic was used to write many Germanic languages. Futhorc was eventually replaced by the Latin alphabet.
One of the earliest surviving works in Old English is by Caedmon, a late seventh century monk and poet. Although he was said to be highly prolific, his only surviving work is "Caedmon's Hymn", which supposedly came to him in a dream.
There are versions of "Caedmon's Hymn" in Northumbrian and West Saxon.
The Northumbrian version:
Here are the West Saxon, Latin, and Modern English versions:
All our knowledge of Caedmon comes from St. Bede's Ecclesiastical History of the English People."
The Lord's Prayer in Old English:
The most famous work in Old English is "Beowulf", which I will leave for a separate post. For now, here are a couple of great (and very extensive) Beowulf sites:
Here is an Old English to Modern English Translator: