Sir Frederic Madden KH (16 February 1801 – 8 March 1873) was an English palaeographer.
Born in Portsmouth, he was the son of William John Madden (1757–1833), a Captain in the Royal Marines of Irish origin, and his wife Sarah Carter (1759–1833). From his childhood he displayed a flair for linguistic and antiquarian studies. In 1826 he was engaged by the British Museum to assist in the preparation of the classified catalogue of printed books, and in 1828 he became assistant keeper of manuscripts. In 1832 he was elected a Fellow of the Royal Society. At the age of 32 he was made a knight, entitling him to the initials KH after his name, and in 1837 he succeeded Josiah Forshall as Keeper of Manuscripts. He did not get on well with his colleagues, and retired in 1866.
Madden was the leading palaeographer of his day. However, his ignorance of German prevented his ranking high as a philologist, although he paid much attention to the early dialectical forms of French and English. His minor contributions to antiquarian research were numerous: the best known, perhaps, was his dissertation on the spelling of Shakespeare's name, which, mainly on the strength of a signature found in John Florio's copy of the work of Montaigne, he contended should be "Shakspere." This led to a lengthy debate and to a period when the "Shakspere" spelling nearly became the norm.
On his death at his home in St Stephen's Square, London, he bequeathed his journals and other private papers to the Bodleian Library, where they were to remain unopened until 1920.
He edited for the Roxburghe Club Havelok the Dane (1828), discovered by himself among the Laudian manuscripts in the Bodleian Library, William and the Werwolf (1832) and the old English versions of the Gesta Romanorum (1838). In 1839 he edited the ancient metrical romances of Syr Gawayne for the Bannatyne Club, and in 1847 Layamon's Brut, with a prose translation, for the Society of Antiquaries. In 1850 the magnificent edition, in parallel columns, of what are known as the "Wycliffite" versions of the Bible, from the original manuscripts, upon which he and his coadjutor, Forshall, had been engaged for twenty years, was published by the University of Oxford.