Adelgitha is a tragedy by the British writer Matthew Lewis. It premiered at the Theatre Royal, Drury Lane on 30 April 1807 having originally been published the year before. The cast included Henry Siddons, Robert William Elliston, George Frederick Cooke and Jane Powell while the incidental music was composed by Michael Kelly. It was one in a run of Gothic plays Lewis produced following the success of The Castle Spectre. The play is set in Otranto around 1080 which was ruled over by Robert Guiscard following the Norman conquest of southern Italy.