Christum wir sollen loben schon (Christ we shall praise splendidly),[1][a] BWV 121, is a church cantata by Johann Sebastian Bach.

The cantata is scored for four vocal soloists, a four-part choir, and a Baroque instrumental ensemble of cornett and trombones to reinforce the voices, oboe d'amore, strings, and basso continuo.

[1]: 106 The source for the text is Martin Luther's hymn "Christum wir sollen loben schon",[3] a German translation of the Latin "A solis ortus cardine", c. 430.

[1]: 112  The librettist created a sermon in versed poetry, devoting the first three free movements to the miracle of the birth of Jesus and the other three to the believer's reaction to it.

Bach scored the work for four vocal soloists (soprano (S), alto (A), tenor (T) and bass (B)), a four-part choir, and a Baroque instrumental ensemble of cornett (Ct), three trombones (Tb), oboe d'amore (Oa), two violin parts (Vl), one viola part (Va), and basso continuo.

[1]: 110 In the following table of the movements, the scoring, keys and time signatures are taken from Alfred Dürr's standard work Die Kantaten von Johann Sebastian Bach.

The opening choral motet, "Christum wir sollen loben schon" (Christ we shall praise splendidly),[1] is built on a quasi-church mode cantus firmus in the soprano.

The tenor aria, "O du von Gott erhöhte Kreatur, begreife nicht, nein, nein, bewundre nur" (O you exalted creature of God, do not understand, no, no, just marvel),[11] is composed as a modern da capo aria, in which the symmetrical scheme is broken up by irregular periodising and harmonization.

It ends with a "startling enharmonic progression – a symbolic transformation" to C major,[2][5] instead of the expected F-sharp minor, to illustrate the closing words about the wonder of the birth of Jesus.

The bass aria, "Johannis freudenvolles Springen erkannte dich, mein Jesu, schon" (John's joyful leaps already acknowledge you, my Jesus),[11] is almost dance-like, portraying jumps, reflecting the movement's references to John the Baptist leaping in his mother's womb during the Visitation of Mary.

The closing chorale movement presents the doxology, "Lob, Ehr und Danke sei dir gesagt, Christ, geborn von der reinen Magd" (Praise, honor, and thanks be said to you, Christ, born from the pure maid),[11] in a four-part setting.

It was probably inherited by his son Wilhelm Friedemann Bach, and went, via other owners, to the royal library in Berlin, together with four parts.