From the LCMS website:
The Augsburg Confession, the principal doctrinal statement of the theology of Martin Luther and the Lutheran reformers, was written largely by Phillip Melanchthon. At its heart it confesses the justification of sinners by grace alone, through faith alone, for the sake of Christ alone. Signed by leaders of many German cities and regions, the confession was formally presented to the Holy Roman Emperor Charles V at Augsburg, Germany, on June 25, 1530. A few weeks later Roman Catholic authorities rejected the Confession, which Melanchthon defended in the Apology of the Augsburg Confession (1531). In 1580 the Unaltered Augsburg Confession was included in the Book of Concord.