The cantatas composed by Johann Sebastian Bach, known as Bach cantatas (German: Bachkantaten), are a body of work consisting of over 200 surviving independent works, and at least several dozen that are considered lost. As far as known, Bach's earliest cantatas date from 1707, the year he moved to Mühlhausen, although he may have begun composing them at his previous post in Arnstadt. Most of Bach's church cantatas date from his first years as Thomaskantor and director of church music in Leipzig, a position which he took up in 1723.

Working for Leipzig's Thomaskirche and Nikolaikirche, it was part of Bach's job to perform a church cantata every Sunday and holiday, conducting soloists, the Thomanerchor and orchestra as part of the church service. In his first years in Leipzig, starting after Trinity of 1723, Bach regularly composed a new cantata every week, although some of these cantatas were adapted (at least in part) from work he had composed before his Leipzig era. Works from three annual cycles of cantatas for the liturgical calendar have survived. These relate to the readings prescribed by the Lutheran liturgy for the specific occasion. The last known cantata was composed in 1745.

In addition to the church cantatas composed for occasions of the liturgical year, Bach wrote sacred cantatas for functions like weddings or Ratswahl (the inauguration of a new town council). His secular cantatas, around 50 known works, less than half of which surviving with both text and music, were written for academic functions of the University of Leipzig, or anniversaries and entertainment among the nobility and in society, some of them Glückwunschkantaten (congratulatory cantatas) and Huldigungskantaten (homage cantatas).

Bach's cantatas usually require four soloists and a four-part choir, but he also wrote solo cantatas (i.e. for one soloist singer) and dialogue cantatas for two singers. The words of Bach's cantatas, almost always entirely in German, consist mostly of 18th-century poetry, Lutheran hymns and dicta. Hymns were mostly set to their Lutheran chorale tune. His chorale cantata cycle contains at least 40 chorale cantatas, each of these entirely based on text and tune of such hymn.