A Scratch Messiah, People's Messiah, Come Sing Messiah, Sing-it-yourself Messiah, Do-it-yourself Messiah, or Sing along Messiah is an informal performance of Handel's Messiah in which the audience serves as the unrehearsed chorus, often supported by a carefully prepared core group. Orchestra and soloists are usually professionals, though their services are often donated for charity benefits. The "scratch" name derives from the idea of cooking or building from scratch.

Messiah is an English-language oratorio composed in 1741 by George Frideric Handel. The text was compiled from the King James Bible and the Coverdale Psalter by Charles Jennens. It was first performed in Dublin on 13 April 1742 and received its London premiere 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.