voluntary association of German Reformed churches founded at Marburg in 1884 to aid Reformed churches and to conserve the Reformed heritage in Germany. It was organized by Reformed pastors and elders who met to commemorate the 400th anniversary of the birth of the Reformer Huldrych Zwingli.

The Reformed League founded religious journals and institutions for the education of Reformed clergy. During the National Socialist (Nazi) era (1933–45) and World War II, it worked with the Confessing Church, the organization set up by German Protestants to resist the attempts made by the National Socialists to control the churches. After World War II, the Reformed League adopted a new constitution and continued as an important influence in the Reformed churches.

Most of the Reformed congregations of the Evangelical Church in Germany are members of the Reformed League.