Messiah (HWV 56)^{[1][n 1]} is an English-language oratorio composed in 1741 by George Frideric Handel, with a scriptural text compiled by Charles Jennens from the King James Bible, and from the Coverdale Psalter, the version of the Psalms included with the Book of Common Prayer. It was first performed in Dublin on 13 April 1742 and received its London premiere nearly a year later. After an initially modest public reception, the oratorio gained in popularity, eventually becoming one of the best-known and most frequently performed choral works in Western music.

Handel's reputation in England, where he had lived since 1712, had been established through his compositions of Italian opera. He turned to English oratorio in the 1730s in response to changes in public taste; Messiah was his sixth work in this genre. Although its structure resembles that of opera, it is not in dramatic form; there are no impersonations of characters and no direct speech. Instead, Jennens's text is an extended reflection on Jesus as the Messiah called Christ. The text begins in Part I with prophecies by Isaiah and others, and moves to the annunciation to the shepherds, the only "scene" taken from the Gospels. In Part II, Handel concentrates on the Passion and ends with the "Hallelujah" chorus. In Part III he covers the resurrection of the dead and Christ's glorification in heaven.

Handel wrote Messiah for modest vocal and instrumental forces, with optional settings for many of the individual numbers. In the years after his death, the work was adapted for performance on a much larger scale, with giant orchestras and choirs. In other efforts to update it, its orchestration was revised and amplified by (among others) Mozart (Der Messias). In the late 20th and early 21st centuries the trend has been towards reproducing a greater fidelity to Handel's original intentions, although "big Messiah" productions continue to be mounted. A near-complete version was issued on 78 rpm discs in 1928; since then the work has been recorded many times.