BWV 248a is a lost cantata composed by Johann Sebastian Bach in 1734 or before.
Only one of Bach's cantatas was printed in his lifetime and many have gone missing. In the case of some of Bach's missing scores, we still have the text, but in the case of BWV 248a the text is now lost. Little therefore can be said about the work, even its title is unsure.
Its existence can be deduced as some of the music was borrowed for the Christmas Oratorio BWV 248 (written for the Christmas season of 1734). The section in question of the Christmas Oratorio (that for the Feast of the Epiphany) has festive scoring with trumpets and timpani. Some sources describe BWV 248a as a lost church cantata (which would fit with other known parody sources for the oratorio), but there has been speculation that Bach may have written the work to honour a Saxon royal, possibly to welcome the new elector to Leipzig.