"O Lamm Gottes, unschuldig" ("O Lamb of God, innocent") is an early Lutheran hymn, with text and melody attributed to Nikolaus Decius.

In both contexts, the hymn has often been set to music, prominently as the cantus firmus in the opening chorus of Bach's St. Matthew Passion.

In his Braunschweigische Kirchen-Historie, Philipp Julius Rehtmeyer [de] presented a Latin report from 1600 that identified Decius the author of the hymn's text and melody and of "Allein Gott in der Höh sei Ehr".

[2] Decius's work is dated 1522/23,[1] in the early Reformation, before Martin Luther's first hymns, published in 1524 in the first Lutheran hymnal.

Though mocked amid Thine anguish; Our sins Thou bearest for us, Else had despair reigned o'er us: Have mercy upon us, O Jesu!

[7][8] The hymn appeared in 1616 first in a Catholic hymnal, in Paderborn, then in the Groß Catholisch Gesangbuch by David Gregor Corner.

[7] It was included in 1938 as "O du Lamm Gottes unschuldig" in the collection Kirchenlied as the only Agnus Dei song.

[7] An ecumenical group, Arbeitsgemeinschaft für ökumenisches Liedgut [de], worked in 1973 on a common version, which appeared in the Catholic Gotteslob in 1975 and in the Protestant Evangelisches Gesangbuch (EG 190.1).

[10] Johann Sebastian Bach mostly used the Zahn 4361a variant,[11] for instance as a cantus firmus in the opening movement, Kommt, ihr Töchter, helft mir klagen, of his St. Matthew Passion.