"Requiem in D minor" is a choral composition by Wolfgang Amadeus Mozart, written in 1791. It is one of his most famous works and was left unfinished at his death. The piece is a setting of the Roman Catholic Mass for the Dead, known as the Requiem Mass, and features a blend of orchestral and vocal elements. The composition is notable for its emotional depth and complexity, showcasing Mozart's mastery of counterpoint and harmony. It includes several movements, such as the "Introitus" and "Lacrimosa," which convey themes of mourning and reflection. The Requiem has since become a staple in classical music repertoire.