Singet dem Herrn ein neues Lied (Sing unto the Lord a new song), BWV 225, is a motet by Johann Sebastian Bach.

It may have been composed to provide choral exercises for Bach's students at the Thomasschule.

[3] Robert Marshall writes that it is "certain" that this motet was one heard by Wolfgang Amadeus Mozart when he visited Leipzig's Thomasschule in 1789.

Johann Friedrich Rochlitz, who graduated from the Thomasschule and remained in Leipzig to study theology in 1789, reported ten years later that Johann Friedrich Doles (a student of Bach, who through 1789 was cantor of the Thomasschule and director of the Thomanerchor) "surprised Mozart with a performance of the double-choir motet Singet dem Herrn ein neues Lied by Sebastian Bach... he was told that the school possessed a complete collection of his motets and preserved them as a sort of sacred relic.

The editor of both volumes is believed to have been Johann Gottfried Schicht, Thomaskantor from 1810.