Requiem, by Johannes Ockeghem (c. 1410 – 1497), is a polyphonic setting of the Roman Catholic Requiem Mass (the Missa pro defunctis, or Mass for the dead). It is probably the earliest surviving polyphonic setting of any requiem mass. It is unusual in that the movements vary greatly in style, and each uses a paraphrase technique for the original Sarum chant. It has five movements for two to four voices and is one of Ockeghem's best known and most performed works.
Ockeghem's Requiem is often considered incomplete as it lacks a Sanctus, Communion or Agnus Dei. The closing movement, the Offertory, is the most complex. Blank opening sections in the Codex imply that there may have been another movement. The circumstances of its composition are unclear; it may have been composed for the funeral of Charles VII in 1461; an alternative hypothesis is that it was written after the death of Louis XI in 1483.