The Mountain Sylph is an opera in two acts by John Barnett to a libretto by Thomas James Thackeray, after Trilby, ou le lutin d'Argail by Charles Nodier. It was first produced in London at the Lyceum Theatre in 1834 with great success.
Often (mistakenly) cited as the first through-composed English opera of the 19th century,[1] it was Barnett's only great success on the stage out of some 30 operas and operettas, and was perhaps the most effective work by an English composer in the style of Carl Maria von Weber. Rarely (if ever) performed in the last century, its plot was parodied by W. S. Gilbert in his libretto for the Savoy Opera Iolanthe (1882).[2]