Aethelwulf was the elder son of King Egbert of Wessex.
He was born some time around 800AD in Aachen, and succeeded his father as King of Wessex in 839. He fought the invading Danes, whose raids increased considerably. Aethelwulf achieved a major victory of the Danes in 851 at "Acleah", probably Ockley. Aethelwulf also allied himself with Mercia to defeat Cyngen ap Cadell of Wales.
In 855, after the death of his wife Osburh (mother of Alfred the Great), he went on a pilgrimage to Rome with a younger son, Alfred. During this visit he also re-married, to Judith, the 13(or 14)-year-old daughter of Charles the Bald (who, notably, was actually crowned as his queen, as opposed to simply bearing the title).
This page was adapted from a page found on the wikipedia at http://en.wikipedia.org/wiki/Aethelwulf. Some of the material about Judith was inspired by an entry in Carr's Dictionary of English Kings, Consorts, Pretenders, Usurpers, un-natural Claimants & Royal Athelings.