Earl of Cardigan is a title in the Peerage of England, currently held by the Marquesses of Ailesbury, and used as a courtesy title by the heir apparent to that Marquessate, currently David Brudenell-Bruce, Earl of Cardigan, son of the 8th Marquess. The Brudenell family descends from Sir Robert Brudenell, Chief Justice of the Common Pleas from 1520 to 1530. His great-grandson, Sir Thomas Brudenell, was created a Baronet in the Baronetage of England, styled "of Deene in the County of Northampton", on 29 June 1611. On 26 February 1628, he was raised to the Peerage of England as Baron Brudenell, of Stanton Wyvill in the County of Leicester, and on 20 April 1661 he was further honoured when he was made Earl of Cardigan, also in the Peerage of England. On his death, the titles passed to his son, Robert, the 2nd Earl, and on the 2nd Earl's death to his grandson, George, the 3rd Earl, the 2nd Earl's only son, Francis, Lord Brudenell, having predeceased his father.

Marquess of Ailesbury, in the County of Buckingham, is a title in the Peerage of the United Kingdom. It was created on 17 July 1821 for Charles Brudenell-Bruce, 2nd Earl of Ailesbury.