Earl of Arundel is a title of nobility in England, and one of the oldest extant in the English peerage.
It is currently held by the Duke of Norfolk, and it is used (along with the earldom of Surrey) by his heir apparent as a courtesy title.
Its origin was the earlier grant by Henry I to his second wife, Adeliza of Louvain, of the forfeited honour of Arundel, which included the castle and a large portion of Sussex.
After his death, she married William, who thus became master of the lands, and who from about the year 1141 is variously styled earl of Sussex, of Chichester, or of Arundel.
In his 1834 book on the earls of Arundel, M. A. Tierney (chaplain to the duke of Norfolk) maintains that the first incarnation of the earldom was with the House of Montgomery.