Sir John Harington (1560-1612) is well known to students of Elizabethan and Jacobean history and literature as a courtier and wit, and as the author of an unusually diverse oeuvre, including a translation of Ariosto; letters; epigrams; and a satirical discourse on a primitive kind of water-closet of his own invention. The Sixth Book of Virgil's Aeneid shows him in more serious vein, and throws new light on his abilities in translation, criticism, theological discussion, and social comment. The original manuscript was prepared for the use of Prince Henry in 1604. Long thought to be lost, it is here published for the first time, and forms an important and interesting addition to the canon of Harington's published writings. The manuscript consists of 162 neatly written pages, containing an epistle to King James I, parallel English and Latin texts (the latter added, after the first eight lines, by a scribe), marginal explanatory notes, and a `comment' in seven chapters. Dr Cauchi has prepared a critical old-spelling edition, with an introduction and commentary.